I recently upgraded my F14 system first to F15 and then F16. The system has been running for quite some time on F14 and is very stable - never experience any random crashes/hangs/etc.
But once I booted up F16 the first time, the system acts as if I've got some extremely flaky hardware - I've had flaky memory in the past and it's similar to that except this seems more like CPU errors or something. I've seen Machine Check Exceptions, and a ton of different OOPS before the system locks up. It doesn't take long, either.
But the strange thing is - when I boot into the F15 kernel, all is well! System runs fine, no issues, etc (well as long as i disable kms, anyway, but that's another issue).
Kernels specifically in question:
Anyone have any ideas? Haven't yet started trying different boot parameters: http://fedoraproject.org/wiki/Common_kernel_problems