I've XT thumbies, drivetrain, RS3 cranks and M950 hubs on my Karate Monkey 29er. Like all my bikes ( engage smug mode ) I can go to friction option. Some old stuff ( SHOCK HORROR! ) just works better.
Bits on the modern are retro - Cooks seatpost, Salsa rasta skewers, RF Next carbon cranks (the proper ones!), and the oldest 9 speed XTR rear der. so it looks like M950 also has flat bars on it for that XC jey boy look (but probably undone by the 180mm discs and Marz Bombers though! Its a Ti hardtail so it kind of suits the older stuff - the basic outline of the shape is no different from a mid nineties Rocky (sloping TT etc)
I say go for it, and remember: [yorkshire] "they dont make them like they used to!" [/yorkshire]