I own all three of the flextail tiny mattresses, and recently took this and the R09 on a cold canoe camping trip to try them both out. The R05 (regular/large) is shockingly comfortable. Like really, really comfy. and I'm sure it would have done great into just freezing temps (but I tried the R09 for those).
It's vertical fill lines, when just deflated a hair below full, force you back into the center/let you feel the edge just enough to keep you on the pad all night. I side sleep and never bottomed out (160lbs). It's pretty quiet, and holds air well.
The problem? If weight and space are an issue, go up or down on the R03 or R05. Probably why there's no other reviews. This is hands-down the most comfortable pad in the line-up and will work all year for most people. But, it packs to 3x (at least) the size of the other two, weighs more (it has a cotton liner inside) and takes up more space in the tent. If I was hiking, this would never work, but we're canoe campers, so we can pack a few more luxuries. This will be my go-to for mid-season camping whenever space/weight allows.