Ok, in no particular order:
WindowsXP is pretty much Windows200 v 1.1. Those saying W2k is simpler... I'd say it's some nice tweaks, but you can set it all back to "classic" should you wish. I wouldn't install W2k over WXP given the choice, but the differences are fairly minimal.
I find Mac OS 10 more sluggish than Windows XP. I have used 10.1, 10.2, 10.3, and now have 10.4 on a MacBook.
If you have more than 26 running processes on a desktop with no programs open (ie after boot), you can lose some stuff. Pointless tray icons, services, whatever. If you have a laptop, it's probably 30, with the power management stuff the manufacturers provide.
"Nobody buys rubbish products" good god did you ever use windows 98?!? Now THAT was awful.
Linux is complicated, flaky and so disjointed in some things - truly not ready for normal users. Hello, changing screen resolutions when you plug in a new monitor? Awful! Sure, if you know what you're looking for. Dependency hell, one-thing-breaks=another. OS X is unix done right (except compiled for size, not speed, and too much UI over responsiveness - but then I want a computer to respond as I click, not after a small delay).
Windows XP on, oh let's say a 1.5GHz desktop with 512Mb or more and a half decent 7200 rpm hard drive shouldn't be sluggish. It isn't sluggish. If it is, then something else is the cause. Clean out, defrag, uninstall, disable.
Oh don't get me wrong, I go through anti MS phases, but the fact is they are so big it's like being anti-government - you can dislike some bits, but most people are probably at least trying to do a decent job. A micro-civilisation. Not "evil" just "human"... demonising them doesn't help.