I'm not into the entire nitrogen hype, more so for bikes. By not having to check you tires as often, your not going to spot signs of a problem you would by looking at the wheel and tire as often. That's why I always tell people to clean their bikes as often as they can. You tend to spot stuff before it gets bad.
This all started with aircraft, moved along to service vehicles such as fire trucks, then to cars, and now bikes. The flucuation in pressure is true, as is the leakage. Nitrogen also helps preserve rubber, but would be no good to tires with tubes in them. It would only help preserve the tube. As for 20% higher tread ware.......... check your tires every time you get on the bike if you don't ride daily, or every other day if you do, and you'll get the same 20% better ware.
The most neglected thing I see on a daily bassis is tire pressure. It cracks me up to hear a customer ask if I did something to their suspension because the bike handles so much better after an oil change
If you do this, remember to have the tires set to about 3 to 3.5 PSI higher then you would normally set your tires cold being the heat normally generated causes the pressure to go up a few Lbs once your riding.
I only know one person who has done this. He works for a car dealer, and gets it for free.
