Rock Band 2 actually has a lot more polish than the first. I don't see the point behind the successive Guitar Heroes, however, and I certainly won't dish out 60 dollars for a track pack.
That said, it is pretty frustrating when the only Motorhead song to choose from is "Ace of Spades". "Overkill" is available on Guitar Hero World Tour - too bad that sucks - but releasing track packs for **** nobody's heard of surely makes less money than a Motorhead track pack. Music, to me, is like oil, for the most part. I use it up. Motorhead is analogous to hydrogen fuel cells. Rock Band is therefore incredibly difficult for me to enjoy unless I have at least a few other people over.