there was a great SAE paper I read on the subject as many of my customers were asking about it, I did a little research.
1) The fact that an uninflated tire actually has 14.5 ( approx) psi in it: atmospheric pressure means that there is still a large percentage of straight air in the tire when its inflated with nitrogen thus negating the anti corrosive aspects of the theory. It is dam nearly impossible to evacuate all air from a tire without pulling the tire off the rim bead therefore dam nearly impossible to inflate a tire with 100% pure nitrogen.
2) in order to meet the claims of being non corrosive, the nitrogen must be medical grade 100% pure. As little as 1% oxygen in the mix and it loses the anti corrosive properties.
3) non of the currently marketed commercial nitrogen generator tire inflation machines is capable of producing 100% pure nitrogen ( most are 80% pure or less ) so in essence, they are useless other than generating gross profit for the user.
4) any thing over 5% air in the tire greatly dimminishes the thermal stability of a nitrogen fill.
Conclusion, worthless to the average person. Profitable for the tire store and the machine manufacturer.