Hey Jeremy, we got quite a few responses to my informal "top innovations" list. And I like your comment. It's true. The self-inflating Therm-a-Rest pad, like the Trail Lite Pad ($60), really changed the equation for camping out. Easy to use, no pumping or blowing needed (well, maybe a little to get it lump-proof).
But I regard it as more of a refinement of what was available. Go back several decades. Choices were poor. Open-cell foam pads were bulky and had poor insulation, and they weren't that comfortable. Air mattresses were comfy but heavy and poorly insulated. Closed-cell foam blue pads, i.e., the Ensolite pad, were light, not badly cushioned (especially if doubled), and superbly insulating. I have talked to big-mountain climbers who were avidly hitting the peaks when the pads were introducedfor them, it was a HUGE improvement. You now could sleep on ice in negative-20-degree weather and have some protection beneath you (other than a sleeping bag). I remember the change myself. On a Rainier climb in June, the closed-cell foam blue pad made all the difference.
And despite gains made since their introduction, they still have a use. Cut a length off for a butt pad. Great place to sit, and useful as an emergency split, all at a weight cost of a few ounces.