Okay... I'm gonna go at this slowly...
1) No it's not... N2 is 14 grams/mole, and O2 is 16 grams/mole, go look at a periodic chart... N is 7 and O is 8, diatomically speaking, 14 and 16 respectively. 1.429g/L and 1.251 g/L densities respecitvely. Basic Chemisty folks...
2) Okay, maybe the nitrogen is dry, but any decent tire shop should have a dryer on the air lines anyway. Go one further, when's the last time you saw a tire shop EVER mount a tire dry? They always put the soapy water slime stuff on the bead to get the tire on the rim. Some of that ends up in the tire. So much for dry... Besides, when't the last time anyone had a tire rust off the rim?
3) If it's so much better for tire life, why don't they offer extended warranties for it, or specify N2 for filing only? Marketing hype. They run cooler, okay, how much cooler? I don't mean according to jim bob's tv show either.. look what 20/20 did to GM's exploding fuel tanks, to get them to explode, and the ensuing lawsuit from GM.
4) Air's not flamamble either... it's the hydrocarbons that are surrounded by it that burn or oxidize. If this has been used for the last 30 years, how come we haven't seen any wide spread use of it, or gov't mandate for automotive use? (they're always up for useless regulations)
Proof is in the pudding though, and if Red's gonna have it done, we'll see soon enough, he should be getting 20 MPG and handle like a vette...
The big claim to fame is even tire pressure according to the website. Okay, so quit being a lazy ass and check your tire pressure like your supposed to. Looks to me like the major problem is moisture, which I can see being an issue. So again, run a decent air drier, and you're fine. Although nitrogen is 3x10 to the -9 power (that's 0.000000003) meters larger in diameter, I can't see any major differences in how long it's gonna take for your tire to go flat.
Sorry don't mean to go off, but something this "dense" really irritates me. Check out the information on the two elements.
http://en.wikipedia.org/wiki/Oxygen
http://en.wikipedia.org/wiki/Nitrogen