I've run games on a dual boot system for more than 10 years. For a long time, I had to dual boot for other applications as well. Now, the only thing tying me to Microsoft are games.
Even those are slowly beginning to become available on multiple platforms. I can now limit my purchases to Linux or multi-platform games first (DropTeam, Savage2, UT2004, Enemy Territory, X2:The Threat, Doom III, etc), Windows games that can run in Linux usingTransgaming's Cedega or Wine second (Civ4, HL2, etc), and Windows only third (BF2, America's Army,GalCiv2?).
Trust me, it's not much fun to have to boot into Windows once or twice a week just to play a game. I would far rather remain in Linux as much as I can. I find it a much nicer environment to use day to day than Windows. So, I personally would be a very happy camper if we can run GalCiv2 under either Wine or Cedega. Failing that, I'll consider putting it on my Windows partition. Assuming that I like the demo, anyhow.