As a Kubuntu use (and I appreciate this isn't strictly a Linux problem), I've found most of the window managers quite buggy on Linux - system clock freezes, menus crash, settings occasionally reset themselves randomly. You allude to driver issues which certainly can happen on Windows, but I've had quite a few in Linux - particularly with network adapters. Let's not even get into gaming on Linux... I do it, but it certainly doesn't 'just work' for many things.

I think there's something to be said for the consistent experience that Apple and Microsoft achieve by being the arbiter of their entire stack.