ZDNet has been following a problem with Vista's MP3 playback and network performance problem. It's the digital equivalent of walking and chewing gum at the same time. With Vista, if you play back and MP3 and attempt to move anything across your network connection, then your network connection takes a severe hit (up to 90% performance degradation) until the MP3 finishes or is otherwise stopped from playing.
Call me silly, but I put a higher personal priority on network performance than playing back MP3s. If you want to play MP3s, then buy an iPod. That's what they're for. Or buy a Mac. Or run Linux on that Intel hardware you're currently running Vista on. I've never seen any problems with Linux handling multiple tasks, especially tasks involving networking and multimedia.
I'm going to have to run some network and MP3 playback benchmarks on Linux, or else find someone who has. Stay tuned.