When I stopped in the Apple store, I played with it for a minute. It looks limited but that is only because it is really simplified. You can do just as much with that program as any other. Since Apple bought out E-Magic, Garageband has some features similar to Logic Audio.
I don't make beats with it, but I am in the middle of raiding its loop library. They got tons of dope classical loops as well as other electronica loops and stuff. You can score the expansion packs pretty easily off torrent sites.