Look, I've used a LOT of OS's. My default choice is Windows, but I also have Mac OS X and Ubuntu installed on my primary PC.
However, your notion that Linux apps are superior is just wrong. If OpenOffice were so great then it would be the de-facto standard. It isn't. Have you ever tried to work with the business card templates in OpenOffice? Nightmare...pain in the neck...maddening. Work with the template in MS Word and it's easy. FireFox vs. Internet Explorer? Each has pros and cons, but I stick with IE because I just want the web to work. I don't want to get to a site and find that FireFox doesn't work, and then launch IE to use the site. So, I just use IE all the time. RDP? C'mon... I can see your point with SSH, but GIMP? If GIMP were so great then again, it would be the de-facto standard. Professionals use Adobe Photoshop, not GIMP. Whether they use Adobe on Windows or Mac, they still use Adobe. I don't like Adobe stuff myself, I think it's over-priced bloated crap that crashes too often, but hey, I don't have to use it so I don't. I'm not familiar with F-Spot or Transmission, but I do know that Evolution is NOT superior to Outlook. Evolution is cool, and it can do MOST of what Outlook can, but not all. Ever tried using Evolution with RPC/HTTPS for "Outlook Anywhere" function? It might work, but then again, it might not. It might be able to connect for direct Exchange access, but then again, it might not. Outlook is the business standard for a reason. It's a mature and capable application.
Your comments about security might be accurate to an extent, but not completely. The idea that Linux is more useable is just wrong, though. Can I use it to play the latest DirectX games? Hmmm...not so useable after all. Burning coasters can happen without regard to OS or app being used, and has more to do with the stress on the machine during the burn process.
Again, I like Ubuntu. It's got some cool features, and has really brought Linux to a whole 'nuvah level. I've been using Linux for over 10 years, and it just keeps getting better. I've turned a few friends on to Ubuntu, and they like it too. But I'm not burying my head in the sand and pretending it's mana from Heaven. Windows is still my primary OS even if I can boot into anything I choose. My wife and kids? Windows all the way. They don't want to hear anything about Mac or Linux. They want their games to work, so they use Windows.