thermarest camping pads??

does anyone have one of these? Or a thermarest equivalent? I want to get one of the pretty cushy car camping types, probably the base camp model.
Are those self inflating mats good for camping? We'd be using them either in a tent, or in the truck.
How are they for side sleepers, or is it pretty much best for back sleeping?
I'm thinking I could get one, and look into making a fleece liner for it, that I could pop it into.