Thanks Donna --
There are some improvements over 6.3.3 -- but not dramatic -- and in some ways it is slower (though reading ImportedItems is enough faster that it is probably worth it). I still have the 6.3.3 install files, but I don't suppose there is any way to roll back the database.
We have done multiple data conversions, so I can tell you data could be reverted to 6.3.3. Depending on several different factors, it would be an alternative.
Hopefully AC will grasp how hated their security "Improvements" have made it impossible to have a ready fail-over server, unless you are using virtualization so that you can clone.