I did an upgrade from F11 to F12 x86-64 using the DVD on an HP
S3300f. It went fine except that the installed called my drive
/dev/sde instead of /dev/sda. It still installed Grub properly. But
it had hd(0,0) /dev/sde in /boot/grub/device.map. I believe this
would have caused problems with any upgrade to Grub.
I suspect that the problem with the drive letters was because the
desktop has a built-in USB 4 slot card reader that were labeled
/dev/sda through /dev/sdd.
Mikkel
--
Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!