Did you fedup from FC17 to FC18? Did that go well?
I did on two machines.
First machine no issues that amounted to anything.
Second machine due to how grub2, grubby and the kernel command line interact I had command line args in my working copy of grub.cfg that got blown away when I followed the suggestion of running grub2-mkconfig. Took me a bit of time to sort all that out.
However lesson learned, now all the grub components are in sync and I’d definitely do a cat /proc/cmdline prior to upgrading and make sure that post-upgrade I got the same cmd line.
Went pretty smoothly, but I had to accept the default partitioning (was using the Beta) since it kept crashing during the partitioning phase of the install.