I'm sure I've seen Nitrogen discussed here - try a search.
Anyway, the consensus seems to be that it's helpful mainly for those who habitually don't check their tire pressure and so let it decrease. I'd estimate that most on this board check pressure more frequently. The higher nitrogen content and reduced water and oxygen leak out much slower so the tires keep pressure longer. The resulting maintained pressure supports all the other claims: reduced sidewall flexing, increased tread life, reduced rolling resistance to improve mpg.
For a conservatively oriented discussion of the benefits of very high pressure, have a look at
Driving Under Pressure: Editorial & Features at Officer.com
You have to make your own decision on psi of course. My son has 44 psi-rated tires and I recently put them up to 41, knowing he'd be bent out of shape if he ever found them pumped like mine.
Mine are also sidewall rated at 44 psi and I keep them around 50. They have 12K miles on them so far and treadwear is very nice, thank you. No complaints from passengers either, not regarding stiff ride anyway.
I measure pressure when cold in the a.m. It will increase about 4 psi from highway driving and also about 1 psi per 10 deg. F temp increase. They can take it.