In RTS i play for fun... I only play them on lan with friends so there's no need to win... :)
In CS I purely play for the competitive aspect, like training and trying to win :D
They say something about the demo in this article
http://money.cnn.com/2004/08/12/commentary/game_over/column_gaming/index.htm
Doom3 runs on most pc's, it has lots of settings you can disable to boost fps.