I received the following error:
Failed to fetch http://archive.canonical.com/dists/hardy/Release Unable to find expected entry gutsy/binary-i386/Packages in Meta-index file (malformed Release file?)
The way to fix it is to remove/disable all the non Ubuntu repositories, also all Gutsy non-official repositories. The later - because the updater probably replaces only the official ones and has issue with the non-official ones.
So currently the new packages are downloading.. and we'll see tomorrow :)