I've been practicing every day for 8 years now with some sort of a Windows OS. At some point you gotta realize that Windows is not perfect and it's not just what users do to it. If you were just to install the OS and have no user interaction (no programs installed, no updates, etc), then yes it would be perfect . . . until you realize it's not doing anything for the user.
I thought MS got it right with Windows 7, but after only having it installed for 6-8 months, I saw a huge decrease in overall performance. I reformatted and reinstalled, saw a night and day difference in boot up time, game performance, etc. I think it's all because of the registry that just gets clogged up over time.
Heck, even at work, my poor Dell workstation with Win7 gets so slow over the month I can't even work anymore. Funny thing is that I have a handful of apps that I use all day (Adobe Acrobat, Photoshop, IE, Chrome, ConnectWise, Office 2010). Why should just those programs slow my system down like crazy?
Windows is great, no doubt. I like being able to play PC games. However, it's nowhere near as perfect as most of you put it up to be.