The pump sack from Sea to Summit is a useful piece of kit, but it's really only if you have a small pad. I tried using it on a REI Flash pad which is 72"x20.5". The pump sack fit perfectly and was fairly easy to use. It's not however a straightforward air bellows. It is obviously soft sided, so collapses in a random way rather than the way a stiffened bellows would. It should also be noted that this will only work with the flat round air valves and not the "normal" air pad valves. An adapter might be available.
As for efficiency, I pumped for 10 minutes, and although the pad was fairly full of air, I found I had to blow into it in order to inflate it fully. This kind of defeats the purpose of having the pump sack. It can double as a stuff sack, albeit a small one.
I'd recommend this to someone who has a torso pad, or doesn't mind constantly pumping the bag to fill the long pad up.
This review was written in the old system and had content requirements that are different than reviews written today.