My own preference, at least this week, is the Big Agnes Q-Core, which is decadently comfortable and not overly heavy. They're about to release an "SL" (superlight?) version that's half a pound lighter, which puts it in the same weight range as many of the Thermarest self-inflaters. (Lori - aren't you using this pad fairly often, too? Your review on Backpack Gear Test was what prompted me to look at it - that and the look of sheer bliss on the face of one of my buddies who had one.)
The Q Core is the most comfortable mattress I have.
I have a NeoAir (original) that runs a close second. The Exped Downmat 9 has vertical tube baffles that are not as comfy for me as either the Q Core or NeoAir, but slight underinflation helps. The Exped would be my choice for temps lower than 5F. The NeoAir has been comfortable for me (in practice) to below freezing a number of times. The Q Core I would trust to the rated 15F, and would be easy to supplement with a foam pad for lower.