Niner frames run large - I am 6' 0" with a 34 inseam and I ride a Medium RIP9, its the only Medium bike I've ever owned (check out the geometry - http://www.ninerbikes.com/rip9 - note that Al's bike has a one degree steeper head angle than what is in those charts). I swapped bikes with a friend on a medium Nomad and it was like a minibike compared to my bike.

I know it sounds like I'm trying to sell the RIP9, I'm not, but I do like mine!