I can sympathize with hesitation over buying a sleeping pad or air mattress. I've recently been looking at my choices in that area and have yet to see the perfect match for my desires. My only advice is that REI has a very generous returns policy, so if you buy something there and it fails to give you satisfaction, you would not be stuck with a failed item.

I was going to add some remarks similar to BZH's. Success in backpacking is just a matter of carrying a pack up a trail to a destination and enjoying the experience. Everything else is just a refinement.