Product review (4 stars): The pros & cons -- mostly pros, but this is a real change in lifestyle for some users, and it's not going to satisfy everyone.
Adding a few notes to my very long review (included below) from 2016:

My happiest discovery is, for those using this device in their shower stall or tub, to get a full-sized (~12.5" x 19") milk crate and prop the WonderWash on top of it. Put the crate so that its length crosses the width of the tub (I can do this with about 2" clearance); the curvature of the tub cradles the milk crate and keeps it from moving forwards and back as you crank the handle forwards and back. Using a milk crate as a pedestal saves me from having to stoop forward and downwards; now I can crank the handle while -- admittedly -- kneeling, but in a back-friendly erect posture. Elevating the WW also makes it easier to pull the heavy, sopping-wet clothes out of the unit. This makes for a HUGE difference in comfort and exertion, with no more backaches!

I also use a bit more water at a time than what I originally recommended -- as much as 3/4 full. But to do this safely, you'll need to reinforce your WW's flimsy plastic frame first (I wrapped mine in duct tape -- and after 20 months, it's holding up fine).

How much detergent to use?  Roughly a palm's worth, to which I add another palm's worth of detergent-boosting washing soda. I've experimented plenty with both "20 Mule Team Borax" and Arm and Hammer Washing Soda", and I much prefer the latter (I think the laundry dries smelling fresher), but YMMV. If you prefer the Borax, stick with that.

I will use the same load of wash water for up to FOUR TIMES -- when the clothes aren't too dirty or dye-shedding. (To do this, you'll obviously want to progress from whites to darks.) I do add some hot water, detergent and washing soda as I go along, to maintain the original water level and soapiness. This saves time and money, but I make sure that every item gets a generous, clean, warm rinse -- and many items, like terrycloth towels and other cotton items -- get rinsed twice. But I don't have to give each rinsing the full treatment (45 spins in the WW) -- just some plunging and squeezing in a bucket to get the bulk of the soap out for the first rinse is fine. I do spin everything after each rinse in the Nina spin dryer, although for items due a second, proper rinse, their first spin will be less complete and a lot shorter than that final, drying spin cycle.

To save some more time, money, and effort, when removing laundry from the WW, dump it straight into a large colander on top of a cheap plastic bowl or tub of a similar size. Pressing is a lot quicker and easier (if less thorough) than squeezing the water out while holding the sopping-wet items over the open mouth of the WW. You can dump the drained water right back into the WW to re-use it on the next load.

I absolutely wash my terrycloth bath towels in the WonderWash -- but this has become much easier since replacing my old ones with new, lightweight, energy-efficient/quick-drying towels. The only difference between the old-fashioned and new- towels seems to be that in the old ones, the loops were attached to a thick backing layer. The new towels manage to hold together despite being almost all-loops, with minimal backing. The loops themselves are just as big and fluffy! (I found good quick-drying towels at Target, for $4 each -- but that's hardly the only store where you can find that category of towel in that price range.) Anyway, these towels spin-dry much dryer than my old ones, and air-dry much faster.

For Nina spin-dryer users, it's probably a good idea when ending a spin to crack that lid open, then let it expend most of its energy coasting while it gently slows down of its own accord, without forcing a more abrupt stop until after it spins out for a good 20-30 seconds. To do this without having to hover over the unit holding the lid just so, find something cheap and unbreakable with some weight to it and a slide-resistant bottom that ideally fits into the wide, shallow groove on the lid, and rest that object on the lid. (I use a small vinyl-clad wire basket that I use in the bathroom as a storage catch-all.) To prevent it from slipping down and off of the dryer lid, I affixed two clear, self-stick silicone bumpers onto the lid.

Most Nina dryer users have probably figured this out already, but just because the WW limits the size of a wash load to, roughly, two pairs of lightweight pants and a couple of T-shirts, doesn't mean that we can't consolidate these tiny loads in the dryer. I frequently combine clothes from more than one washing load's worth in the spinner, saving quite a bit of time.

As for hanging clothes up to dry, if you don't have the room for a large clothes rack, get a collapsible one. And/or, if your place has dormer windows, you can screw in closet-rod holders on the walls in those narrow nooks and saw 1/2" wooden dowels to fit (I found both of these items at Home Depot, but any hardware store will probably have them) and you've got a quick fix. And when you're done, you can remove the dowel rods and stash them out of sight somewhere.

From April 19, 2016:

I bought this along with Laundry Alternative's "Nina" spin dryer (110V size -- the one with the pink feet) in early December, so I've had them for four months now, and I'll never go back to laundromats.

I've got a few tips for using this unit:
1)  Before you wash your first load, wrap the frame's vertical parts with at least two layers of duct tape. (I also wrapped the bottom corners for extra strength.) It bucks and heaves a bit when half full of water, and I can't imagine it holding up well over time without the extra reinforcement.

2)  You're going to need to use this model (with the pop top) in a bathtub or similar, because it leaks quite a bit around the lid while in use -- anything from a few drops to a heavy spurt, on each rotation. What's more, because of the spinning, quite a bit of this will be landing on you, so you may want to block most of it with an upraised hand (the suction cups can keep it pretty firmly stuck to the tub, so you can generally turn it with one hand without needing to hold the frame still), and/or wear an old T-shirt or bib or something. Definitely not any shirt you want to wear immediately after outside the house! (Side note:  I use my Wonder Wash in the bathtub, which necessitates kneeling on the floor and/or squatting for a couple of minutes at a time. You'll want a nice, thick, spongy bathmat or similar for your knees, and all the kneeling/squatting and leaning and bending over -- as in pulling out the wet, heavy clothes and squeezing out the excess back into the barrel -- may be too arduous for persons with bad knees or backs.

3)  Remove the plastic plug-thingy from inside the tub and toss it -- along with the draining tube -- in the trash. The plug catches on clothes and comes loose with some frequency, making a loud rattling sound as the tub is turned. Don't worry, the bottom is reliably watertight without it. (I think its purpose is to keep the clothes from clogging the drain while emptying via the tube.) The Wonder Wash leaks way too much to use it anywhere but in the bathtub, shower or outdoors. I was hoping to use mine on the kitchen counter top next to the sink, or on a wheeled kitchen pantry cart that I could wheel next to the sink, but those are out of the question. The upside of this is, since I'm stuck with using it in my bathtub, I can drain the Wonder Wash by flipping the barrel upside-down. This is 10X faster than waiting for it to drain slowly through that tube, with the clothes obstructing the flow (even with the plug left in...).

4)  I also recommend getting several cheap plastic salad-type bowls, the kind of thing you can get for $1-to-$3 at discount stores, for holding your mini-loads of laundry in its stages of washed, wrung or spun but needing a rinse, etc. I use my Wonder Wash along with the Nina spin-dryer, but I'll do about three loads of laundry using the same wash water, depending on how well it's holding up, of course. You'll also need a narrower, taller one to catch the water from the Nina spin dryer, if you're using one.

5)  You'll get your clothes cleaner and use less detergent if you boost your loads with a small amount of washing soda (not washing powder, but soda, like this:  [...]). This is especially so if you're laundering white items, stained items, or washing in hard (mineralized) water. The washing soda assists in stain-busting directly, but it also binds with the minerals in the water, which helps the (tiny quantity of) detergent do its thing.

6)  I've only used hot water so far, and I'm not tempted to try otherwise. I spin-wash most of my items 120 times (about two minutes), and the combination of hot water and washing soda is removing the long-term stains in my white cotton athletic socks and the armpit stains in a couple of ancient white t-shirts. So yes, if you use this unit as specified (plus a little soda), you can get your clothes cleaner than many laundromat machines ever get them!

7)  Fill it to no more than the halfway line with water, and try for a 50-50 ratio of water to clothes. The fragility of the frame makes it important to not go much beyond that line, and the clothes need space to slosh and roll around in order to get thoroughly clean, anyway.

8)  The Wonder Wash uses a graphite lubricant around the axle/shaft and sheds black flecks of it, which runs down the sides of the barrel and onto one's base surface (another great reason to use this in the bathtub or shower stall!). While I don't think this lubricant stains clothes, you'll have to take care to not let washed clothes flop down and into it as you squeeze them dry. Four months on, and my unit is still shedding specks of graphite (or whatever it is).

9)  There's a fair amount of lint in the dirty wash water, and if you simply pour this down the drain, it'll eventually clog it up. So far I've been using two wire-mesh drain protectors, but I'm going to try pouring the dirty water into a cheap (thank you, dollar-store!) colander with the filter from a new HVAC HEPA air filter instead. That ought to do it!

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General impressions:

Reservations about the frame's strength and the leaky lid aside, it's a great unit to have for anyone looking for an alternative to laundromats, doing laundry by hand in the kitchen sink (which is more time-consuming than this, yields variable results, and is hard on one's hands) or energy-intensive washing machines in general, out of principle. Yes, you'll save money, you'll be lowering your personal carbon footprint, and this device treats your clothes with more TLC than many regular washing machines, but the single greatest benefit is not having to choose between going to the laundromat every two weeks or having dirty laundry piling up. Now I always have what I want to wear ready to wear, and with very little piling up of dirty laundry. Granted, now I have damp laundry hung up or laid out on racks in my apartment two or three times a week, but that's an improvement over the full hampers and even bags of dirties on the floor which I used to have.

Having both the Wonder Wash and the Nina spinner makes it possible to home-wash sweaters as frequently as they need them, knowing that they won't get torn up by a harsh clothes washer mechanism, shrink in a heat dryer, or sit out for a solid two days drying at home (they dry in one day or less now -- much, much better!)

I also find this combo especially valuable in washing bras (tip:  hook them before washing, to keep them from catching on things) and the wool-blend socks I wear in the northern-US winter... no more tearing up lingerie bags in laundromat machines, losing socks in washers, or inadvertently shrinking those socks if they stay in heat dryers too long!

As for capacity, I'm able to wash and spin-dry my fuzzy (polyester fleece), full-length bathrobe. For sure, it fills both the washer and the dryer, but both (barely) manage to handle it. And being polyester, the bathrobe is completely dry in a couple of hours or so, even in my cold apartment in the winter. Terrycloth bath towels are no problem -- just do them one at a time. Some people have posted that they can't do sheets in this unit, but I find it's no problem doing sheets one at a time -- but mine are only "Full"-sized. To dry, I drape the sheets (one at a time) on a wheeled clothes rod/rack, over plastic clothes hangers to spread the two halves apart for faster drying. Works like a charm.

Then there's considerations of quality and comfort:  busting old stains with the aid of the washing soda (which I only started using with the Wonder Wash, fearful it needed it.) Not wearing out my fingertips doing laundry in the sink, or wearing out my hands and clothes by harsh hand-wringing. (I squeeze the excess water out before spin-drying them.) Granted, hang-dried laundry is unsightly and somewhat inconvenient, and some fabrics tend to dry stiff or wrinkled. Bath towels are quite stiff after drying, but they soften up again with the first use.

Not to overlook the environmental & economic considerations:  no more trips to the laundromat. Using much less detergent. Using minimal energy to dry clothes, although you may need to set a portable heater near them in the winter, if you keep your place as cold as I do. (On a related note, drying clothes at home during the winter humidifies the air quite nicely, although the extra condensation on windows can lead to mildew under them if you're not careful...) No more lost socks or heat-shrunk wool items. Less wear-and-tear generally, esp. if you spin-dry the clothes prior to hanging them up to dry.

The one thing this unit (along with the Nina spin-dryer) won't save you is time, if you are accustomed to doing huge batches of laundry all at once at a laundromat. This product washes mini (or micro-) batches of laundry, and you'll still have to squeeze & wring them dry, or spin them and then hang them up or lay them out on drying racks. And it won't be long before you run out of handy doorways, shower rods, and other places around the apartment to hang up damp/wet clothes. On the other hand, it beats going to the 'mat every week, if that's your pattern.

And a final outcome of my new laundry system:  I used to keep a lot of clothes around as fallback items to wear after using my favorites. I dreaded laundromat sessions so much, I'd put them off and the dirty laundry would pile up to a ridiculous, unseemly extent. This week, I culled one closet of least-favorite shirts, since I don't need to keep them around anymore. I've got two more closets to cull, and then I'll be donating this stuff to charity.