I run presta on my roadie, to handle 100psi ofcourse.
Trucks run Schraeder valves at 125psi.
I was lucky enough to buy a job lot of tyres a few years ago from a guy who used to work at the LBS. He was an early adopter of 29" and bought every new tyre at trade price as it came out, rode it a bit, then bought the next one. I bought the whole lot off him, I think I paid £200 for 23 tyres with hardly any wear. I'm still working my way through them, which means I rarely have matching front and rear tyres on any bike.
I generally run my tyres at 40psi, which everyone tells me is too high, but then I tend to think of my 29er more as a 'cross/touring bike with flat bars and front suspension than an MTB, so I go for speed on the hard bits over grip on the loose bits.
Worcestershire's fastest veteran vegan mountain bike endurance racer with a beard.