I have noticed this with the past 3 beta versions - when you upgrade to the most recent version it leaves the start menu and desktop shortcuts of the previous version behind and you have to delete them manually. I just upgraded to 1.6 and had 1.5, and 1.4 shortcuts still there and had to delete them manually.
Oh and I just checked my Add-Remove programs list and all 3 versions I have had are still there.
Yeah, as you note you’ll need to run the uninstaller prior to upgrading to a new beta release. In fact, I’d do that just to be on the safe side. Wipe out all three installations so you have nothing left, and then re-install the latest.
I thought that the desktop shortcuts were left over and deleted/made new ones a few versions ago. But my son paid no mind to them, and when he rebooted, the shortcuts were right. I’ve done the same thing since then (his is XP and mine is Vista) and it works. You just need to reboot.