I have had and used one of these Ridge Rests for years and it's still going strong.
I don't for one minute imagine it's as comfy as an inflating matress type but it does the job,is much better than sleeping straight on the ground, insulates fairly well and unlike a thermarest will not puncture.
I imagine that as I get older my bones and joints will cry out for a little more padding so we will see !!!!

http://www.rei.com/product/708520