I would normally stay out of this, but frankly this is one of those topics driven by myth. As previously stated, air is 80% nitrogen. So, if you are a nitrogen fan, you get 80% free. Oxygen, the other main component of air, is no more likely to leak out of a tire than nitrogen. The atomic weight of nitrogen is actually slightly lighter than oxygen. That would make it more likely to leak if the composition of a gas has anything at all to do with inflation.
There are no credible studies (other than suspect ones cited by pro-nitrogen groups) that show any real benefit of nitrogen inflation. Just sayin'