I'm in pretty much exactly this situation. My livelihood is in Linux, and I've always had a Linux box or two at home, but I ditched Linux desktop around 2004 when I got my first Powerbook and thought I'd never look back. Forget "iOS-ification," boat loads of bugs in Lion and Mountain Lion made me flee back to a Linux desktop. I've been using Fedora 18 on a nice simple tower I built for just that purpose for about a month now and am really happy. My rather new rMBP will probably get loaded with it soon.
I say try a Linux desktop, it's come a long way. I was impressed when even my wi-fi worked right out of the box. I can't think of anything that didn't, though my bluetooth mouse settings seem to sometimes forget themselves and the pointer goes back to default, unacceptable speed.
We have Steam, Chrome(ium) and I bet even Netflix support soon. Also, the guys at Yorba are doing some cool modern apps in Shotwell and Geary. I really like GNOME 3, but of course there are plenty of current options if that's not your thing. If you've been happy on a Mac, you'd likely be just as happy or more with a modern Linux distro than with Win 7.