In preparing for Macaroni Penguins Gig #126 tonight I noticed that my newly updated iTunes 10.6.3 didn't seem to be playing with my py-appscript scripts.
A quick search brought up this posting entitled "The first nail in the coffin of Python appscript", which reveals that new security technologies coming along in Mountain Lion (OS X 10.8) might well stop existing appscript based scripts from working. And anyway appscript itself is no longer being developed or supported, so I fully expect all my useful little scripts to gradually decay into non-functionality over time.
For the time being I have managed to use appscript.terminology.dump() to make a static glue from iTunes 10.6.1 that I can use to allow my scripts to continue to run with iTunes 10.6.3, but it doesn't feel like a robust long-term solution.
Update 2012-09-12: I updated to iTunes 10.7 (under OS X 10.8) and my py-appscript scripts are working again. Hurrah!