RedHot runs nitrogen in her tires as do all of my cars. I have been doing this for quite a few years. Personal experience has been the tires require far fewer 'touch ups' to maintain the air pressure where it should be. I still check my tires regularly with a very accurate digital gauge. Also have found that they drop slower when the ambient temperature drops and heat up slower when I do high speed driving. However this is the first set of run flats that I have done it with. 
