Finished Vice City; it was a nice expansion of the III world, but I thought they should have done more with the ending. After you do all of the property assets, there are pretty much two core missions left, neither of which results in much of a climactic ending. Still, I wasn't disappointed.
I guess I'll pick up San Andreas sometime, but sadly they aren't going to issue IV for the old XBOX and don't think it will translate well to Wii (I got COD III for Wii, and the driving and melee just plain suck.)