I took both the Basic Mugello (Nov 03) and the Avanzato (Jun 04) courses.
You'll find a report in "the other forum" on the
http://www.ferrarichat.com/forum/showthread.php?t=21147, there is also a link there on my prior post on the Mugello course.
In short, it's an expensive but good experience if you can afford it, the Avanzato being a better (more thrills and fun) experience than the base course (which you must take first). The basic course is all about getting you to drive clean. The advanced course is about being faster while staying clean.
A friend just came back from the Mugello course and it seems that things have evolved a bit: you now get a few telemetry charts there too.