It's interesting because the method of "upgrade" which is used when going from RP to RTM is basically a clean install which still migrated all your personal files. I kind of like that idea and think it would be ideal of Microsoft to use a similar method for upgrades from other operating systems, and then devise some sort of solution to get apps reinstalled.
It would sure help avoid a lot of the frustration usually associated with upgrades, such as incompatible apps and driver issues.