Yeah, the R-value is pretty low. If you're camping in the cold (~0ºC or less) it's going to get chilly. That's the price you pay for ultra lite gear though I guess. There are other options that are pretty well insulated, or you can do what I've seen a bunch of people do and stack this on top of a closed cell foam pad (e.g. the thermarest z-lite pad). Kinda defeats the purpose of ultra lite'ing, but it'll keep you warm and comfy.

This is the least expensive of the Thermarest NeoAir pads and designed for 3-season backpacking (anything above freezing). If you want a warmer pad, I would go for the NeoAir All-Season. It has an R-Value of 4.9. This will easily be able to take you to about 0 degrees (if you have a 0 degree bag). It is more expensive, but it uses higher-end materials to get to that rating.