*There are, of course, people who reflexively hate anything MS related, and they post general gripes about Gates, Ballmer, and the way Lyndon Johnson used to act all the time. I know, I'm one of them.
The things I notice most about switching from Mac OS 10.4 and Windows XP are the memory build-up in XP that leads to sluggishness and a restart (whereas the Mac just goes in and out of sleep-mode for months without a hiccup), and window compositing with Windows vs. using the 3D card with Mac OS. It's painful to see a re-draw as you resize and move windows after moving from a mac. I think Vista handles this, but I haven't seen anything above Home Basic (which still has the compositing issue).
Moving from Linux, the first thing I see is the lack of a sane software repository with haphazard apps strewn about on the Mac, and strange cruft on every install for Windows. It seems like each platform gets something right, but a host of other things wrong. You would think that Microsoft was in the best position to fix all their issues, but they can't seem to bring themselves to force people out of old API's to break free.