I have two remaining major issues with Windows, which is down from the remarkably sizeable list that had me switch to Mac and OSX, which makes it easy to keep the Windows box as games only:
+ Extreme monochrome flatness. It's obtuse and hides information, like the edges of icons, encouraging misclicks, and is quite frankly pig ugly. I quite liked aero glass and the UI as Windows 7 had it. The first Windows that "looked right". If only they'd modernised and flattened that a little...
+ Abusive view of the users: Tracking and telemetry you can't easily disable. Knowing better than me when to reboot, to install, when to display ads.
There's lots of minor issues, like 3 to 5 different incarnations of every feature from menus, to dialogues, to preferences. Or Explorer usability. Or how discoverable some things are. Or the whole mess of registry and installing. Or the 40GB of ever-growing Windows sub folders. All I can live with, but ugly and tracking? Much harder to tolerate.
So as ever I'll end up with a mix, rebalanced a little. One day I'll have a lovely seamless all-something world, but it hasn't happened since the 80s when it was Amigas everywhere. :)