Yes, conceded, installing from scratch is the best method.
However, once your data is backed up, what's to lose by trying the upgrade path and see what happens?
From (64 bit) 12.1 to 12.2 using the dvd upgrade route proceeded quickly and without incident. I have a couple of minor things to address, but end result is excellent. Well done openSUSE.
12.2 is impressve.