I use a Windows machine, Win7 to be exact. (f*cking HATE vista) and I love the crap out of it. Being able to get rid of excess garbage slowing my machine down, (bloatware sucks hard) and able to customize what I want is the best part. I liked XP a TON, but I'm finding I really really enjoy Win7.
I haven't ever built my own computer, but I think I'm going to do that with my tax refund. It should be interesting. The bad part about my netbook is that it lacks the power to play games, and I definitely want to be able to run games on my computer.
Windows machines do have to deal with viruses, but I find that if you are smart about anti virus software, you don't have complete meltdowns, and have to replace your computer.
But then again, I'm also a huge Android fan. I just wish I could understand the SBF stuff so that I could root my phone and be comfortable with doing stuff from the terminal. I don't really understand all that, so I haven't done anything to my phone, though I really would like to get rid of some of the crap the phone makers are forcing on my phone. (ie, Twitter, and not being able to delete the stupid f*cking app)