The new iTunes as far as music goes, isn't really any better than the previous version. Nothing significant was added.

If you manage iPods and iPhones then the improvement to the app organization is going to be a big plus.

I'm not sure if the new store layout requires this new version, but I can see Apple making it that way. Even though the content is HTML and would have presented perfectly fine in the 8.x version.

EDIT: Nice new bug in 9.0... iTunes now mixes together the tracks of multi-disc releases. It used to number the tracks 1..10 followed by 1..10 and now it does 1,1,2,2,3,3...10,10 Arrgh.