C3C runs very smooth under Unbuntu Linux with Cedega making it think it is in Windoze, Civ IV runs pretty smooth as well but has occasional crashes (but less than 10 in a game I played on through 2050). With some more tweaking / testing it should be able to run it more stable.
Right now I've got almost all functionality up and running needed on a daily base. So Browser, e-Mail, chat, MM players, burners and more shit but most important Civ! All is legally free except Cedega which requires a mandatory subscription for 3 months at $15. After that it is free to use but no updates and support.
After installing Ubuntu all of this took less than a week.
Windoze gets fist in arse.