The security flaws in Windows are exaggerated. I have 4 PCs running variously Vista, XP and Windows 7. I have never had a virus or malware problem that wasn't caught and dealt with by the (free) virus checker, and even those incidents are infrequent. There are numerous virus reports on Windows simply because there are numerous machines running it. And numerous idiots using them.
Windows Vista was clunky to begin with, but since Service Pack 1 its fine on 2GB of RAM and runs slightly sluggish on 1GB. This is because Windows has to support an immensely larger range of hardware than OSX, it would be impossible to optimize for every combination. I have an XP machine that has an Athlon 2000 in it and its running just as well as when I built it 4 years ago. Its had a motherboard and hard drive failure (neither are Windows fault), both of which were cheap to replace.
Get a life if you think OSX is so much better than Vista. You have been entirely brainwashed by Apple into believing there is only one way of doing things. I am still mystified by why maximise on OSX does not make a window fill the screen, and why closing the last window of an application doesn't exit that application. Double clicking an icon on a desktop in Windows is one click more than opening the same application off a dock, and Windows has quicklaunch if you want to save yourself one click.
So much is made of Expose in OSX, forgetting that Windows users don't need this feature because the Taskbar shows every application that is running. The Dock and Expose are very selective about what they show. Why does a style conscious company like Apple only allow me the choice of two colours for my windows? OSX is supposedly more consistent than Windows, but installing an application on OSX is sometimes an install routine, sometimes the app has a little applications folder and sometimes it doesn't. Getting both those Windows to the foreground on my 1024*768 desktop is pain in the arse with Expose.
OSX is nice for sure, and its nice not to have to install antivirus (though you really should, because even though Macs can't catch viruses they can pass them on through email), but to use it is to be entirely dictated to by Apple about which hardware you use, and how you use your OS. I like my G4 iBook very much, but I also have a 1.6Ghz Celeron laptop running Windows 7 that will do everything it can but it lets me choose what software I install and putting a new CD drive in it won't take me half a day.
Oh yeah, build your own, because if you want to play games, Apple are *****.