We are talking about the music library program, not the online store here. As for the question, I say 'a resounding NO', for the reasons that it forces me to duplicate my library, is horrably glitchy, and is another example of Steve Jobs trying to steal our freedom. Forcing me to use it is not very endearing either.
Edit: I run it on a Vista rig, and get nothing but grief for it. Its probably ok on an Apple
Edit: I run it on a Vista rig, and get nothing but grief for it. Its probably ok on an Apple