I agree Pete - I actually reckon Metallica has been a roaring success partly to the ( also great ) success of the ACDC machine......I think ACDC sales numbers gave them a real 'roll on' to create another music pinball and thank god they created a machine that 99% of people are really liking , in all it's versions and for loads of reasons.
I am sure they would be thinking to create even more music based games down the track
BUT I do think they need to 'space them out' in between other concept titles.
Congrats to Stern - I also think they will follow Metallica with a CRACKER as they have now ( in a good way ) built a rod for thier own back