I used Macs in school for years but couldn't afford my own until spring 2008. One of the first things I did was install boot camp because I was nervous using a Mac full-time. I fired up boot camp several times over the next year—mostly to play games. Now I haven't had to use it since 2009. I can't think of a single piece of software, aside from some games, that I would ever need Windows to run.
A few years ago when I got my current job I had to use a PC for a few months before getting my fancy 27" iMac. My productivity was terrible during those months. The only Microsoft products that I have to use daily are Outlook and Lync and both are pretty terrible—at least the 2011 versions. Outlook likes to stop fetching my mail during the day and for some reason I can no longer view team calendars, even when they re-invite me. Lync randomly disconnects without telling me so people can't chat with me. Luckily I've got my team using Trello now which helps!
The only Microsoft thing I really liked was my Xbox but the Xbox One has been a cluster. It's so unstable, surprisingly slow for a newer console, and the software is really clunky. First party games like The Master Chief Collection have been a disaster. Even after countless patches I still have to force quit the game about once an hour or so because matchmaking craps the bed or the menus glitch out and I can't navigate anywhere.