I was a CO2 hater until I was teaching a flat fix seminar and actually used one. Wow. In the approximately split second it took to inflate a tire, my whole lifetime of sitting by the side of the road looking like I was masturbating while actually only manipulating a mini-pump didn't even have time to flash before my eyes.

But I still don't trust that new-fangled technology, so I compromised with one of those hybrid pumps other people already mentioned--will take a CO2 cartridge, has a built in regulator; is also a mini-pump.

If I'm playing mechanic volunteer on an event ride, I bring a frame pump. As a commuter, running puncture protection tires, I'd feel perfectly comfy with a chuck and a couple of CO2 cartridges.