I started using CO2. I carry a couple of cartridges. I have an inflator that uses non-threaded cartridges, which can be had cheaply at XMart or sporting goods stores. I also carry a mini pump on longer rides, just in case. I always have two tubes and a patch kit (or a spare tubular and a can of Pit Stop). I carry them in a seat bag, which at least one forum member takes to mean that I'm not serious about riding.
Just remember that CO2 will leach out of the tube quickly, since the molecules are small, so deflate and refill with a standard pump when you get back to base.