Back on topic, in my (limited) experience, I've certainly found Windows the best in terms of usability for audio. Should note, I've never used MacOS, but compared to Linux on the same it's been all one way traffic:
1) First and foremost is the software support:
a) Gapless playback is an absolute must, and for whatever reason the people who are working on gstreamer don't seem to get this.
b) While I don't mind getting to grips with a few programs in depth to do specialised tasks, generally work or technical related, for simple audio playback this isn't the case and there isn't an, as yet, usable simple player for Linux that I've found. I absolutely can't stand the "media library" type programs, which seem more focused on people whose collections are single songs rather than albums, have little access to tags other than Artist/Track, and have things like,eg, "Ratings" systems. (I know if I like a track, I don't have to remind myself.) In general, the most developed Linux programs seem to be of this kind, not withstanding mpd, which I've not even once managed to configure...
c) all widely used professional software is Windows based (and Mac?), and that won't change anytime in the near future.
2) Straight out-of-box hardware support, no operating system can touch Windows at the moment, although Ubuntu (I have most recent experience with this distribution, but have tried Red Hat and Mandrake in the past) has made huge inroads recently, especially with Hardy. Case in point, new motherboard had onboard Realtek chip, and it took me a complete recompile of the audio core in Linux for it to work. For the vast majority of potential users, this is simply unacceptable and certainly was frustrating.
All, of course, do have room for improvement!