Did you upgrade or format/install? I'm pondering it now. I've had quite a few system hangs lately and am wondering if I should even attempt the upgrade to 12.10
Ultimately, blowing away the compiz configs (rm .compiz*), a dpkg --configure -a fixed the AMD driver and boot-repair from a Ubuntu LiveCD was a wonderfully simple way to redo grub.
Not painless but not particularly difficult to fix.
Migrating was painless, except for finding enough disk space on an external drive to move all my somewhat disorganized and sprawling file hierarchy.