I've been looking a bit into CO2 pumps, but also into using nitrogen (or rather, nitros oxide) to inflate the tires.
I've done some searching here and on the Internet about using nitrogen. Most people say it doesn't matter much, and I'd probably generally agree. However a few things about nitrogen don't seem to be mentioned when people have discussed using it with bicycle tires.
Firstly, I can get unthreaded N20 cartridges cheaper than unthreaded CO2 ones:
http://finewhip.cart.net.au/store/ni...-5-charge.html - $1.41 each
http://finewhip.cart.net.au/store/co...-16g-x-10.html - $1.69 each
(both exceptionally cheap when you compare them with bike/tool company branded ones)
I'm thinking of buying a Topeak One Timer pump, which can take both threaded and unthreaded cartridges, so I think it'll fit the unthreaded N2O cartridges above.
Secondly, apparently nitrogen is less prone to expansion under heat than normal air is. I wonder if this would be beneficial under heavy braking when the rims heat up, and therefore reducing the chances of the tube popping. Roads can get pretty hot here in Adelaide in summer (greater than 38C/100F air temperature is common enough), so nitrogen in the tubes might help there as well.
Thirdly, with less oxygen in the tube, they might last a bit longer, although it's probably negligable enough that it's not a major advantage.
Finally, there doesn't seem to be any comments about whether nitrogen suffers from the fairly rapid deflation that CO2 seems to.
It looks like it's cheaper to use N2O, so I might have a go with using it anyway. However I thought I'd also see what people thought here.