i have something similar to this
http://koolatrononline.stores.yahoo.net/koolatron-p75-kool-kaddy.htmlbut mine has wheels at one end and a handle and was not as much (paid something around $100). Says 4 amps. Mine has a thermostat (not adjustable) and at that amp rate would probably need to recharge the battery after 24hrs if you don't open it too much or reload it, sooner if you do (and also depends how hot it is outside).
equivalent size ARB fridge takes .85 amps, so drains a lot less, so should be a no brainer - one thing i can't find is what is the minimum voltage at which it will work (not mentioned and that sucks since it's important esp on camping trips where you dont run the engine).