Well, I've decided to revive this topic after actually getting ahold of the beta (more like an alpha) leak.
The Havok physics are all in place (almost everything works perfectly), most of the graphics are really impressive. However, I have one really big drawback. I have a GeForce 4 MX420, so I don't have pixel or vertex shaders. So I get either no water, or this really silly metallic looking stuff.
Even in alpha form this "game" runs at full speed on my 2.3 GHZ P4 with that MX420. All in all, very enjoyable. Although I don't condone what was done, I'm still going to take advantage of it.

I'll still buy the full game. This really is crap in comparison.
I haven't yet converted HL1 onto the HL2 engine. Apparently the improvements are lighting, shadowing, water, and havok physics. So pretty cool. If I get that up and running I'll tell you.
Did anybody else get this?