Just started it last night. This is freeware for your computer. Free. And it will basically run on a calculator. From what I have played so far, it's very solid. Impossible Mission meets Splinter Cell. Go download it right now. It's like 20 megs, will play on any computer from this decade, and is really fun. One warning: for some reason the start up load time is really, really bad.
Here's a link to a video.
http://www.youtube.com/watch?v=z1dLNLji5n0
I'm also playing Team Fortress 2 and Avadon: The Black Fortress, both from Steam. I 'll have more to say about all three.
In spite of what I said to Steerbotnik lately, perhaps I am becoming a PC gamer afterall.