Just a warning,
I just updated from 6.72 to 6.73B2 (I skipped B1), and watched as my entire download list and wish list vanished! I still have my list of completed files, though, so it didn't clear everything. I know the beta page warns about upgrading from a version prior to 6.60 without clearing those lists first, but I'm thinking you might want to just change it to state that for ANY version upgrade.
Oh, and I didn't have any files in the failed download list, so I'm not sure if that would have cleared or not.