since it has MIDI (v4) i use it for composing. it's much more intuitive to use compared to cubase or logic. It's also good for mixdowns, cause of its routing possibilities. And it's good for whatever you want to do with music, exept for djing (i mean djing as a "disk" jockey ;)) and scratching.
it's a DAW now, so it can do a lot! go to
www.ableton.com and take the tour or download the demo version.