Personally, I really like Windows. XP was simply epic, fast and quite flexible; I really can't find a downside to it. Vista had quite a few downsides but those were solved pretty quickly after Vista's release, and SP1 basically fixed any real bugs it had. Win7 looks very promising but I've yet to be able to use it myself so I can't really talk.
I have used a ton of flavors of linux, BSD, and I'm pretty familiar with OSX too even though I've never owned a Mac. They're all nice and have their strong points which is why they're deployed in different situations.