I picked up this X5 from theblue (friend of mine) about 3 years ago. It's still kicking. I have 195K miles on the odometer.
So far I had to do brakes, replaced rear air springs with coils, front drive shaft replacement, valve cover gaskets, alternator, ignition switch, rear bushing refresh, fuel pump (only repair that left me stranded!), and now I'm diagnosing a pretty bad vibration at 60mph under load... It's been fun, but I'm looking to upgrade to an E70 in a couple of months.

Things I haven't fixed that are annoying: pass door handle carrier (can't open from outside), leaking sunroof, too much rear camber, air pump on start up is loud, leaks oil (in lots of places), airbag light.... and others.

Xoutpost has been a great forum for helping me with all the issues above ^