Product review (3 stars): Works, with caveats
When I bought the Norcold, I couldn't decide between it or the ARB 50 quart fridge.  They seem pretty comparable, but the Norcold model is less expensive.  Ultimately, I went with the Norcold unit, despite some shortcomings.

The good:
- It gets cold pretty quickly and is nice and quiet (so does the ARB).
- The lid opens lengthwise, which means that I can open the lid fully when in the back of my SUV (Toyota Sequoia).  The ARB lid opened sideways, which meant that it was too tall to open inside the vehicle.
- The lid is easily reversible, so that you can access it from inside the vehicle on a long road trip and then reverse the lid without turning the entire fridge around 180 degrees, which is nice, because this thing can be really heavy when loaded up.
- This fridge only uses 6 amps to run the compressor (according to the docs), so you can plug it into any of your cars power ports.  The ARB manual states that it requires a 15 amp fuse and that many car power ports are not wired to handle the power requirements of the ARB.  Sure enough, the port in the back of my sequoia was only rated at 120W (10 amps) and would not start up the ARB.
- I like the simple on-off toggle switch.  The ARB switch requires that you hold a button down.
- It's a little bigger than the ARB, but still fits behind my 3rd row of seats.
- There is a nice gap between the handle and the body of the unit to get a tie down strap in there if you wanted to tie it down.

The bad:
- This is NOT an AC/DC refrigerator - it runs on DC current only!  This seems like a complete misrepresentation.  The ARB unit can be plugged into a wall or the car and truly is an AC/DC fridge.  With the Norcold, you'll have to by a large wall adapter to convert the 120V AC in your home to either 12 or 24V DC for the refrigerator, at the cost of another $70.  Plus then, you have another bulky thing to keep track of and possibly lose.  The ARB comes with a standard type of power cord that can be found cheaply at any hardware store in case you lose it (or forget it).
- There is only one temperature setting, so it can either be a refrigerator or a freezer, but not both at the same time (same as the ARB).
- The power requirements are quirky!  When I plug this into the power receptacle in the back of my SUV it works fine when the engine is running.  But when the engine is off, the fridge compressor wouldn't start up.  This was frustrating to diagnose, because the fridge always waits 2 minutes before even trying to run the compressor.  After the 2 minute delay, I could feel it vibrate as it tried to start the compressor and then it would flash an error code relating to fan speed!?  I don't have the same problem when I plug it in up front, so maybe Toyota just has pretty light gauge wiring going to the power receptacle in the back of the vehicle.  Still, this was better than the ARB unit which wouldn't run at all in the back (with engine or not).
- The power cord sticks straight out the side (instead of bending at 90 degrees).  This seems like a weak design.  The ARB had a 90 degree power cord, which seems to make more sense.
- The lid hinge looks pretty weak it's just a few bumps of plastic that hold into a plastic slot.  We'll have to wait and see how that holds up.
- Thetford (norcold.com) won't let you order replacement parts or even download a PDF of the the manual unless you're a dealer!  BOO!

Tips:
You might want to buy a separate auxiliary battery to run this thing when camping so you don't have to leave your keys in the car.
I can't decide between the Arkpak or one of the Goal Zero products.