Garageband is ok, it has a few fx and you can run 2 Au's along with the built in compressor/verb/delay and stuff but theres no grouping or sends as far as i can tell, its quite basic, level's and pans, but it does actually have some automation in there which works surprisingly well, and it isn't actually that bad at editing stuff. It's pretty good for people who only like to dabble a tiny bit i guess. Plus its nice for quickly getting down ideas and the virtual instruments are quite nice for that purpose.
To be honest i think really it was built up mostly for podcasting as it has the kind of interface and editing that suit that really well.