Hope you´re happy with it. For a live recording, I would have recommended a Zoom H2 recorder for US$200 instead of a laptop. 4 microphones, little, easy to carry around, choice between 90 or 120 degress stereo, simple SD cards.
Of course, it depends on what you´re doing and what results you want to get. Carrying a laptop and soundcard and mics around for a stereo live recording is much too complicated, computers are used in the studio. That said, if you want to multitrack or stream live from a concert, best choice may be a laptop.
I´m not a Mac fan, they´re ok but no dedicated fan here. I don´t care what gear I record on as long as it works and the mics and converters are great.
Garageband is shit. Try a standard sequencer/ audio recording program, my choice for Mac would be Logic (Protools is ok but too expensive).