An adsense call in my template caused a fatal error when switching to 2.1. It did tell me what was causing the error. The only solution was to reinstall the old version version, remove the offending code from the template, and then do the new istallation again. The code was then reinserted in the template.
There are other problems. At first all the links categories were lost as were a couple of static pages. After redoing the links categories they have merged with the post categories for links but not for posts.
The insert links panel opens with no save or cancel button and the close window button will not work. Had to close the page. The new autosave worked so all was not lost but it was back to working in code view.
Oh, and I have lost my AdSense delux insert button.