We're having a very late spring in Alaska - I had a camping trip this past weekend that had been planned for a couple of months expecting spring temps but it snowed 6" Friday. We went anyway, and I got to use my new BA Q-Core SL for the first time. Temps dipped into the low 20's overnight.
First the good: I have the long/wide (25") version of this pad. It's extremely comfortable. The 3.5" thickness gave me enough room that I could even sleep on my side without my hipbones punching through to the ground, which is a first for me with an air mattress. I didn't experience my typical back spasms and cramps on this pad like I did with my old ones. It's a keeper, and worth the weight penalty for my purposes.
The bad: It does transmit the cold from the ground pretty significantly. I topped it with a Z-Rest since I expected this to occur, but would definitely not have wanted to sleep on it without a CCF topper to up the R value.