Yeah, I'm excited about it, I'd love to play it. I think that the new engine is going to be far more interesting considering the heightened interactivity of dynamic clipping planes. That's my main anticipation, interactivity. I want to shoot a wooden 2x4 and have it splinter apart as it's load comes crashing down.
Glad I have 2 free copies of HL2 when it's released ^_^