The BEST mat is IMHO the Exped Downmat. They come in 7cm and 9cm thickness, and the 9cm has a R-value of 8. Normal foam pads about an inch is just 2 in R-value.

I have the 7cm and in addition I have the Z-lite foam. We use the z-lite to sit on when taking a break. Because of the bubbles any snow that slides on to this does not end up under you. On flat pads it does. http://www.exped.com/exped/web/exped_homepage_na.nsf then search for downmat.

The only problem is that it raises the person 4 inches, and on some tents with sloping endwalls the feet could end up into the canvas.

I sleep like in my own home bed on the Exped Downmat. For a person like me way over the youth (64) I value some lux, and a good night is one of those.