I have the regular size insulated Tensor pad. I find it very comfortable to lay on, but I don't think the temperature rating is close to accurate.
If 15 F is the minimum, it should be comfortable at freezing. I was cold on two different nights that had forecast lows in the upper 30s or low 40s and definitely did not get to freezing. This was with a 15 degree Western Mountaineering bag that I have used in much colder temperatures, wearing what would normally be more than warm enough.
The other negative is that it is harder to get the air out than other air pads I've had.