i sleep cold - and need the insulation to keep me at a comfy temperature. i've had this bag for 1 year and took it winter camping several times on some 5-6 day trips. with temps way below freezing - frost inside the tent (and on my bag) - i kept nice and warm. I'm skinny (5'5" and 110 lbs), so i don't always touch the sides of my sleeping bag. this was a problem in the past, as i woke up from cold spots when i shifted. but it doesn't seem to happen with this bag. and after repeated stuffings, it has kept it's loft fairly well... only seeming issue is that it seems too sweat a lot. my bag always seemed a lot wetter than my companion's bag in the morning (though i never had a problem w/comfort).
Fast forward to 2011 - so have had this bag for 5 years now, and the bag now has lost most of its loft. i only store it in its mesh bag, but it no longer keeps me warm in 20 degree temps, not even with socks, thermals, and a bag liner in... very sad that when i asked MH about it, they said their synthetic bags only last about 5 years.