A friend of mine pre-ordered the Orange Box, so he had the TF2 beta. I played a bit of that and wow! When I first saw the character design over a year ago, I thought it was rubbish. After playing it, I see why they went in that direction. This is just a really fun multiplayer experience, not a serious tactical shooter. I think they wanted to separate Team Fortress 2 from Counter-Strike, otherwise it's just CS with multiple classes.
I think I'll pick up the Orange Box and give my other copy of Half Life 2 to a friend. I got it for free with my 9800xt many moons ago anyway, and I haven't even played any of the extended episodes yet. As EmperorSteele mentioned, Portal does look great, but I've only seen video demos of it.