FWIW I have given up on Garage Band and moved on to a software called Reaper (by Justin Frankel et al of winamp fame) and set it up to work with midiO plugin and my roland drums. Everything just works now!
http://www.reaper.fm/
OS X support is still in beta but has been working great for me.
Another bump! I'm looking for exactly the same answer :) (routing MIDI-out to my drums via Garageband). Or perhaps some other software equivalent to GB capable of midi-out. Thanks.
nixgeek:
I noticed in ur sig that u dual boot ubuntu... do u use ubuntu for midi stuff?
