I gave up Windows a long time ago, apart from occasionally booting into it for gaming. It's too much of a chore manually unticking boxes on every bit of software to stop it doing annoying spammy stuff (usually to do with systray icons) and even if I'm good at avoiding it there's always the looming malware threat. Plus having to support it and having unpicked people's home computers over the years has put a bad taste in my mouth. All in all I'd rather avoid it at home.
That leaves OS X and Linux. (No "I use AmigaOS you insensitive clod"?)
Usually I get curious about how Linux is doing and go and have a play with that for a bit, as I do love its philosophy. Then something will come up that "should be simple" and isn't, and I get annoyed. I'll grant that for everyday web browsing and printing etc Linux on the desktop is in a much better position these days, and has significant advantages such as built-in drivers for most things and centralised updates so you don't get every bit of software under the sun pestering you to install an update. I love this, it's a godsend and almost worth it on its own.
But there is always something that strays slightly from the mainstream stuff but that "going by all the other OS'es should still be a simple matter" and it never is. That's where you often end up with a number of different pieces of software being involved in different ways (whether they're dependencies for a package or for compiling one) and having to sit and read the man pages for each of them and you're thinking "I don't have time for this, okay I wouldn't have known libfoo2 like the back of my hand but ultimately I could've had it going in 10 seconds on OS X" even if it means paying someone $1.99 on the app store. And so I end up switching back so I can get stuff done.
It basically follows my "interested in hacking around" vs "interested in freeing up my time for other things" phases.