Course it wont do anything bad, it may not boot and youll have to reset the CMOS but thats about it - youre a wizard techie, so you should be able to fix that!
I was able to stay in 3.6GHz for a few hours, until I ran SMP. But I'm back to 3.4, and I plan on going to 3.6 or 3.5 when I get a new case and CPU cooler, because the temps aren't where I like them.