Airmat or a filled pad?
What do I want for a pad? I like the weight savings of a regular no insulation airmat, but dont wish to be cold.
For about twice the weight you can get an insulated one.
But whats to stop a guy from getting the airmat, then putting his coats or something between the ground and the mat and getting a better R value?
It sort of works. But you will have much better results by putting your insulation on top. Unless your sleeping bag completely covers the pad all night, the pad will suck the cold out of the surrounding air and cool you off. With top insulation it doesn't matter if your mattress is cold. But either way you will compress your insulation while it's under your body or under your pad. That's why a thin stiff foam pad is recommended to top the airmat.
The Neo Air uses a reflective foil surface to reflect your body hear back to you. It works a little. I think they claim R2 or better. A friend of mine uses his down to about 20 degrees with good results. Personally, I need more insulation under me, so I bought an Exped Synmat 9. Not cheap, and certainly not light, but I don't carry it far.