Nitrogen over Air - can you feel the difference?

[stevierst]

I believe that racers only use what they call 'dry nitrogen' because the pressure doesn't change when the tyre gets hot due to there being no moisture or other unstable contaminants , and we all know how hot race tyres get!

I know a guy with a Nissan GT-R, and they have the ultra high performance tyres filled with nitrogen. He track races it occasionally, and says he can't feel the difference if he fills the tyres with compressed air.
For the road its probably not necessary unless you ride like Rossi.