I recently did an in-place upgrade of a TFS 2010 RC to RTM box. All appeared to be going fine, all the verification in the upgrade wizard passed, but when I hit configure the first step failed. It said there was a missing dbo.sysobjects in the warehouse DB. I then had to resort the configuration DB as it was partly upgraded to try again as the DB was left partially upgraded.
I got round this problem by telling the upgrade to ignore the reporting side of TFS. The upgrade completed without issue. I was then able to re-add the reporting via the TFS administration console (optional configuration of features in 2010 is really useful!). I actually chose to recreate the warehouse DBs anew to make sure I was bringing over no corruption. Once TFS had rebuild all the DBs and cubes all was working fine.
So the technical tip: if upgrading TFS 2010 and you are getting a problem with the reporting sub system, consider bypassing the upgraded and just rebuilding that system when you are finished