i used to use hand pumps, and then i discovered CO2 pumps. for commuting, there's just no contest between the two in my opinion. after a flat, i can get my tire up to about 120psi in mere seconds with CO2, whereas who knows long it would take me with a hand pump, if i could even get up that high in the first place. and CO2 pumps are MUCH lighter, MUCH smaller, and, well, i just don't see the downside to them, at least for commuting purposes where you'll only ever realistically have 1 flat, 2 at the very most, to deal with on any given trip. if i ever had more than two flats to deal with on a commute, i'd seriously just throw in the towel by that point and walk to the nearest train or bus stop and take transit the rest of the way.

at home i have a nice floor pump for periodic top-offs, of course, but for on-the-road emergencies, CO2 all the way for me. it's so freaking fast; you're back on the bike rolling in a fraction of the time compared to hand pumps.