I’ve been trying out the 2009 version of GarageBand for a few days and it feels tighter than last year’s. There is less lag when you switch between info and loop mode, the same hardware seems to be snappier in most operations, actually.
It seems that the lesson feature is pretty usable, too. The software comes with 16 free lessons for the piano and the guitar. If you have trouble getting into reading dry books, these lessons are well worth checking out.
The way you add effects on both software and real instrument tracks seems more intuitive. I haven’t tried out the “magic band” stuff, but if brings the joy of music to people, why not? (I could almost say the same about Microsoft’s Songsmith, but this is just too weird.)