Despite what I said last year, working completely off a Powerbook does work (now that I have a functioning powerbook of course!). Only one thing mars the experience - high CPU usage from iTunes.
I have a lot of hungry apps open, Fireworks and Omniweb can be quite greedy, but they’re beginners next to iTunes with its range of 31-60%. Obviously, playing music from another source (such as radio or iPod) would solve this, but I prefer being able to play music from my computer. Especially when I have bluetooth niftiness such as Salling Clicker pausing iTunes whenever there’s a phone call.
Playing music is important part of work and home life, but on OS X, there seems to be no alternatives to iTunes. Audion has long since died, and while its still available, its no match for iTunes for managing and playing a library of music.

This is why I’ve been keeping an interested eye on SongBird - an open source XUL based app for playing media. I have no idea whether it uses less CPU, or when a version for OS X will arrive, but I’m really keen to try it. I love what they stand for and the approach they’re taking. I have high hopes! (I also love the sound of this job, shame I’m not qualified! :D ).
So in the meantime, if anyone has any ideas for lower CPU music playback on OS X, or tips to reduce iTunes CPU usage, I’d love to hear them. Have I missed a good OS X alternative?
Update: Some of the comments gave me an idea - I turned off my Volume Logic plugin and CPU dropped dramatically! Aha, culprit found!