I have nitrogen in my Rocker (and my wife's car). Very good ride and better tire wear. Also great because you do not have to check tire pressure as much. I do not watch the mileage close enough to comment.
Same thing I have heard, the Nitrogen is a bunch of Bologna. It's used in aircraft tires because the internal pressure of the tire is not affected by altitude. On car or bike tires it makes no difference in pressure or tire longevity IMO.
Kind of like the paint shield you pay $300 for on a new cage. Might make you feel better but in the end, out of the compressor, I;m putting in 78% like it is. Is it worth the extra $ for me.....No