The cheap one is junk, the Luxury Lite is in a class all it's own, but still prone to a couple of problems.
You still need an insulator pad under you in cold weather and like Stid pointed out, it does even out the ground nicely.
It's low like a pad, works good for tipis and other small shelters but takes the same effort to get up off the ground, unlike a regular cot which you can sit on.
You have to be careful with the bows and the edges, no pressure on them or you will bend or break them.
The feet can also be broken.
I've no idea how Thermarest's customer service is, but the original company that designed, made and sold these had top notch service, never ever tried to dodge out of making things right.
For less weight and just about the same money I got a Exped XP9 which is like 3 inches think, very warm and comfortable.
When I want even less weight in warmer weather, I use my Neo Air all season, soon to be a Xtherm.