M-Audio actually makes a whole bunch of neat stuff. I've had my eye on the
Oxygen 8 for some time; the introduction of Garage Band just makes me hunger for it even more. A little more advanced (and a little more pricey) but even more lust-worth is the
Ozone . That's outside my budget, at the moment, but I can dream, can't I? As far as prices go, both of those can be found much more cheaply than the M-Audio site, but i thought that'd be a good place to link to for the sake of info.
Both of those are smaller keyboards than the one Apple is reselling, but, as you mentioned you have a Powerbook (as I do), their smaller size would also make them much more portable in the even that you ever get into doing live stuff or whatever else.
For that, M-Audio also makes a cute little
backpack that's perfectly suited to carrying one of those 25-key keyboards and a powerbook.
As for myself, I'm leaning very strongly towards the Oxygen 8. I hope that helps and doesn't complicate the search for you.