I have been using Windows and Mac for a while now but the only reason I am sticking around a Windows machine is because majority of my consumers out there are still using good old windows. So, when I create a software or some kind of product I have to make sure it works on windows as well.
Few other reasons I use windows is because Microsoft Office & Onenote are some excellent tools out there. I am still not too fond of the Mac version of the MS Office or haven't really found an awesome alternative just yet. Also, tools like SeNuke, etc... only work on Windows. So, to better manage my projects and or for automatic scheduling I have no other choice but to fall back on a windows.
What is your reason? Do you secretly wish all those great IM related tools out there would work with your Mac?