I've used canned air ($5.50 a can @ walmart) and it'd do about 2 cleanings before I had to buy a new can.... That's $60 a year just for my computer. Well, my dad, mom and brother also have computers that need cleaning out 1-2 times a month... So that's $240 a year in air cans...
I spent a little over $300 at Lowes and bought an air compressor and it works, better than can air too.... No problems so far... Just cant put the nozzle super close to the pc parts since it's got a lot more air pressure.
Have you had any problems with moisture?? water can build up in the tank of a generic air compressor..that's why you'll find the drain valve on the tank.
After working construction on hot, humid days, we would empty the tanks of our 8 hp ~ 20 gallon compressor...we'd usually see about 2 ounces spray out of the tanks.
That was my only concern before I started using my air compressor to clean out my computer...the moisture.