I've been using the Klymit for a couple of years, and Mike has the short version. We used them on the Challenge and back-packing across the Pyrenees. I like a soft bed, and always fuss over choice of mat etc, but the incredibly tiny weight and pack size makes the Klymit absolutely worth using. Of course there are some hints and tips: I take a thin closed-cell foam mat in addition (bought to any length off the roll) as I sleep cold and prefer to use that under the Klymit. This also protects from any potential punctures through the tent groundsheet, but I always do this with any airbed. The neat little pump they provide must be used to get the pressure up, then the mat should be perfectly OK all night. I have occasionally had to do an extra air top-up during the night. Tussocky ground can be a challenge (I had tussocks poking through the holes in the mat on one occasion) but tussocks are a trial whatever you are sleeping on, and you are no more likely to roll off this mat than any other.