Review (3/5): For what it is, it's good.
I was not expecting much when I bought this -- how good can a $10 wax heater be? I'd never used the cartridges, so I figured if I'm going to try it, then I'm going to try it cheaply. So I got this and the Azulene wax.
First thing I noticed was that it was BRUTAL trying to get the cartridge out if it hadn't been heated first. (Protip: don't push the cartridge in all the way. Leave a little space between the roller head and the warmer unit. You'll thank me later.) It took a lot to wedge the thing in there, too. But there again, cheap product, of course it's not going to be perfect.
I can't speak for heating times; I plugged the unit in and kind of left it while I went and made myself dinner so I didn't really time it. Once it got going the wax spread on evenly and thinly, with very little mess (although the edge of the roller gummed up a bit but that was easy to wipe off). It didn't take long at all to do a half leg wax, and the mess was substantially less than the usual pot and spatula method. Definitely NOT for smaller areas, though. It didn't do nearly the job I wanted it to do on the underarms.
I'm not sure this will pull me away from my wax pot permanently, largely because this method seriously limits the kinds of waxes you can use. But for when I'm in a hurry, it does the job. Would also work nicely for travel.