The science is still the science, no matter how many people try to claim otherwise. Assuming you use atmospheric air from a source with an effective dryer to minimize moisture content, you are starting out with almost 80% nitrogen anyway. The oxygen molecules are more reactive than nitrogen, and over time could have an adverse affect on the rubber. Of course the outside of the tire doesn't get a choice, and it's always exposed to not only atmospheric air but also ozone, which is more damaging to the rubber than plain oxygen. Independent testing comparing long term leakage between tires with regular old air and tires with 98% nitrogen have shown a very small advantage for nitrogen, perhaps one or two psi over a year (not mounted on a car, just filled and allowed to sit). And the fact remains that nitrogen loses pressure with changes in temperature at the same rate as atmospheric air. So any claims of never having to check and adjust pressure are suspect at best.
As long as you can get it free, there is no reason to avoid using it. If you have to pay for it, it is definitely not worth it.
Jerry