This is what I do, Win7 for games, debian for work.
I like the dualboot nature as when in debian I have no excuse to startup a game and get distracted, when in windows I know I'm off work and I can relax.
Also having access to good command line tools is priceless - I'm not conversant with powershell, so maybe windows is good for this now, but being able to quickly grep/sed/awk/vi/etc is so useful.
I used to do that, but booting between two OS's was always kind of a pain and really Windows 7 generally just kind of works. I haven't booted into my Linux partition for month. For the times I need Linux there's vmware, but there are relatively few things that I can't get done on windows.
Server side on the other hand I'm all *nix all the time.
I also used to do that, but I landed on the other side - Linux generally just kind of works, and I dropped my Windows partition a couple of years ago. For the times I need Windows there's Virtualbox, but there are relatively few things that I can't get done on Linux. :)