Whenever I see my muso buddies with their Mac laptops, I often do hear the siren song of "It just works". Lately I'm dealing with an issue where I can't get my windows mobile 6.1 phone to sync with my XP SP3 PC. Seems it's a well known issue with this combination. Folks with iPhones, though their wireless service is dodgy, aren't having the same issues and man there are some cool music apps for the iPhone.

Garageband is a killer application when I've seen it in use. Simple and powerful with quite a usable set of plugins (the guitar amp sims and effects are really pretty good). If your white $900 Mac came with the iHome package which has Garageband, you have made a pretty good investment for lappy usability with a great music application to boot.

What are you going to use for an interface? That's where you might get nailed on price. There are some interfaces you can use in both platforms.