I really don't know why nitrogen is put in car tires. An extra cost most tire installers/dealers can add? Some probably just change the valve cap to green and voila, an extra large charge.
Oh, there are plenty of benefits:
(1) Cool fluorescent green valve stem caps (assuming your nitrogen vendor has any marketing savvy), which will look sharp with your spinning wheel covers.
(2) Bragging rights. OK, you were behind the curve with cell phones, iPods, thong underwear, etc. Nitrogen in tires is relatively new to the mass market. Now's your chance.
(3) Reduced fire danger next time you land your space shuttle or commercial aircraft, and tell me you won't sleep better knowing that.
Very good dope on the subject here:
http://tinyurl.com/6gc8rp