i have 2 of the Downmat 7 mats. inflation is a bit of a pain, but it's just as fast with the stuffsack as breathing into it would be, and doesn't introduce moisture/weight. getting the stuffsack attached to the valve takes a little practice...
sleeping on the thing is absolute bliss--the most comfortable pad i've used, and i cannot even begin to detect the snow under me. 3/4 length is great--just put your pack or other misc crap under your feet and lower legs and you'll be fine.