I've used every version of Windows from 3.0 up to Vista. It's a long story, but around 12 years ago when I started having to use Windows at work (mostly NT 4.0, 98, 2000, XP - for software development and systems integration), I started to keep a list of bugs, design flaws and annoyances that I found in Windows. After just 3 years, I had filled an entire notebook with thousands of entries. (I did this to keep from going insane and smashing all the PCs around me, shouting, "Why the f@#$% doesn't this work right?!?")
People who have grown up with Windows probably wouldn't see many of the design flaws (or bugs even) as flaws at all. If that's all you've known or if that's what you first learned on, you'd think it's normal. If you've known better ways of doing things, using Windows can be like a kick to the groin.
Of course, I later found I could make a similar list for the various versions of Linux (which I was horrified to find was even worse than Windows), OSX or any OS out there. I've used or own nearly every major OS ever made - including NeXTstep, IRIX, QNX, BSD, OpenSolaris... and so on. They all have problems. It's just that some have more annoying problems than others and I think Linux and Windows top the list.