That depends entirely on what your goals are. For a lot of my use cases Windows is neither compatible nor easy to use in the slightest.
That being said I have a 50/50 split. The main box runs Win8 because reasons and inside that I've got an Ubuntu VM which I use about half the time to do dev, scripting and scraping.
Personally I think using both Windows and Linux in one machine through the use of a Virtual Machine is pretty much the ideal setup. Linux is just ridiculously powerful if you know how to use it right. Windows just has some stuff you need. They both have their advantages and disadvantages, so by using them both you just get the best of both worlds. I'm 100% satisfied with my setup.