The other day I got a 49key USB keyboard for the mac (I'd seen one in the Applestore in San Francisco and almost bought one then) and it's really opened my eyes (and, well, my ears) to what the Mac is capable of audio wise. Suffice to say that Garageband (a music package) is excellent and the software instruments (both samples & synth) are top-notch.
Because of this I've decided to sell my albeit great Micro-Korg, which seems a tad extreme, but I can't see how I'll use it much from now on since Garageband (and the great Jam Packs) have pretty much everything I could want - and I only tend to doodle with it all anyway. Despite only having the Korg for 3 months, I'll probably (hopefully!) even make a profit on it since I bought it in the USA when the £:$ rate was very good.