I decided to downgrade my iTunes from 11 to 10.7 for a number of reasons, top most was the fact the the new UI drives me barmy!
I followed the great instructions at http://arstechnica.com/apple/2013/03/how-to-downgrade-from-itunes-11-to-version-10-7-on-your-mac/ and found that I couldn't open my iTunes library after the upgrade.
Since I didn't make a library backup before the iTunes 11 upgrade I
thought I would be stuck, but to my surprise I found a
Previous iTunes Libraries folder in my
Restoring was as easy as taking my swapping
iTunes Library.itl with
the file in the Previous iTunes Libraries folder from December and
everything worked fine...
One thing I noticed was that my new iTunes purchases didn't show, but this was a minor inconvenience. Now I have the old iTunes back and I'm happy… for now...