Re:
hey guys, I bought a NeoAir Xtherm a couple of years ago and I've got to say it's probably the best bit of kit I own - it's quite amazing how effectively the technology works really.
I use it with a RAB Quantum-Top sleeping bag which has no insulation at all on the bottom, it's just air+plastic between you and the ground, but I've always been toasty even at just below freezing. When it's much colder I use two 'Top' bags (so still no insulation on the bottom), sleep in base-layers and have always been warm. The heat-reflection thing is so effective that you get the strange, pleasant sensation of being heated from below!
It's also remarkably comfortable and stable, and 'flattens' the roughest, stoniest ground.
I wouldn't worry too much about durability; the new version's tougher than the original and they're quite easily repaired I think. As long as you're prepared to be a bit more careful, you should be 'right. I unpack mine straight into the bivvy so it's never directly on the ground. It's most likely to get a puncture from something sharp in the rucksack (pot supports) so that's something to be careful with.
In the morning if I need to be off quickly, the whole lot, bivvy, mat and bag can be rolled up together and I'm away in 5mins flat.
Regarding inflation, I've never used the sack and haven't had any condensation/mould issues yet. You'll be adding/releasing a bit of air in the early hours with yer mouth sometimes anyway as temperature changes effect the pressure a bit. Probably best to store it partially inflated when not in use.
The only other concern I can think of apart from the slight fragility is dimensions; if you're a big guy you might prefer the widest version - it's been very well designed so you don't roll off the well-supported edges, but the standard width's a bit narrow.
Also, those 3+'' of plushness raises you, and the loss of headroom is noticeable in a hooped bivvy, so could be an issue...
It might seem an extravagance, and extortionate for a roll of cheap looking plastic but if you're happy to be a bit careful you'll be chuffed to bits with the performance.