Team 1771 used an impeller with a CIM motor in 2010 and (I think 2008). I'm not sure of the gear ratios or anything. All I know is that it worked REALLY GOOD. (I remember stories of one of our mentors taking the funnel we used in 2008, put it against a glass window, turned it on, and the window started to warp inwards...

)
As for a quick release-
What we did in 2010 (before we switched to a roller after Peachtree) was we used a "pop-top". Basically a tube that was in the same system as the vacuum, powered by a pneumatic cylinder. When we kicked, it was programmed to pop up, releasing the vacuum pressure for X milliseconds before kicking.