I started playing with Linux as a teenager, back in the RedHat 5.1 days, around 1998. I have used it as my main desktop, or dual-booted between Linux and Windows 98-2000-XP. Back then, I had a lot of time to waste, troubleshooting hardware (remember internal hardware modems?), and just playing with the system. Why would I use just an email client when I could set up fetchmail, qmail, spamassassin and mutt to accomplish the same, right ?
Went from RedHat, to Slackware, to Ubuntu, to Arch.
But the times have changed - I have a job, kids, and I really don't have the time to struggle with Linux anymore. I've tried a couple of modern distributions, but ended troubleshooting the same problems I encountered 15 years ago !
I use Windows 7 on my desktop exclusively. It just works, is stable, and honestly is the best desktop OS I have ever used.
I'm running Linux where it thrives most - DD-WRT on my router, Ubuntu on my tiny odroid-u2 "server", and XBMCbuntu on my HTPC. I can not imagine running anything else on these devices.