I've always had bad luck with upgrades of any kind with any OS. I
decided long ago to try to never do upgrades anymore. So now I back
up my data, wipe my drive and do a clean install. This may not work
for everyone but I think it tends to be the safest way. Even on the
famed OS X, I've heard of people having trouble after an upgrade,
where others using the exact same hardware had none after doing a
clean install. I'm not sure why, but it seems clean installs seem to
go better.