CO2 is great, I use it often, but remember the following equations:
N (number) of flats on any given rides = N of CO2 carts you have + 1

And there is always the possibility of a CO2 mishap that would make you lose a cartridge (happened to me this weekend).

Don't jinx yourself, always carry a pump, especially if you ride in somewhat isolated areas.
Good advise Grog I'm checking out CO2 pumps on Performance right now. Thanks!