Finally finished reading through all those 280+ posts!
I restarted STEAM at 12:01AM and was ready to play at 12:14. Looks awesome with all that detail, and runs perfectly smooth at 1280x1024, maxed settings, on my A64 3200+ w/x800 pro. Somewhat lengthy loading in spite of my WD74 Raptor, but not too bad.
It has a somewhat "stiff", technical feel to it compared to Doom 3, which is much more organic IMHO. Can't really say I prefer either over the other, they're just different. Haven't played more than a couple of hours, but HL2 seems to have more enjoyable gameplay so far. Surroundings are really immersive and pretty!
Also too easy on medium difficulty, as someone pointed out earlier. But it makes for better sight-seeing
I've had a couple of in-game crashes so far, but both just to the desktop so I could fire up the game again immediately.
Will be fun to continue tonight when I come home, after the wife and 7 months old son get their share of me first
listening to http://www.progulus.com/ a mountain stream of progressive, rock and metal