I don't want to incriminate myself, but I can say that I've played HL2. A non-code complete alpha of this game blew just about everything else I've ever played out of the water. This game is gonna blow our collective minds. I can't wait.
I've watched demo after demo after demo online, and if I ever get the chance to play it, I'll probably giggle like a schoolgirl with a crush.
I think my favorite thing about it right now is that it takes place outside, instead of inside where things jump on your back and rip you to shreds before you can turn around and start to tickle the trigger of your shotgun.
I have played the leak as well, and I'll admit, I was a little impressed (well, for it being about half done in the leak), the physics are awesome, though the only level worth playing is the e3 physics testing level.
There was one level I played in the leak that even without the game even remotely done has such an incredible atmosphere to it. THIS IS POSSIBLY A SPOILER, SO STOP READING THIS IF YOU DON'T WANT TO KNOW A THING.
You're going from wall to wall trying to avoid snipers (you can see their laser sights watching for you). You end up in a small shop like building and if you stay there too long, the snipers will shoot through the glass, shattering it (the first time through, this scared the crap out of me). Eventually you end up inside this abandonded warehouse where you see new iterations of the old HL bosses, except this time, they're much more agile, and MUCH more dangerous. If you try and climb the debris and boxes to the roof, the snipers have an easy shot...and if you go to the basement...well, let's just say there's moaning coming from inside the walls, and those walls aren't gonna stay up forever.
If the final game is 10+ hours of this sorta thing, I will never get out of this chair again.
have you guys seen the new CS:Source footage? http://narics.net/cs.source/showcase.php it's down at the bottom, it's shaky cam with annoying korean voices going, but it's about 20 mins of footage! And the game looks awesome! I can't wait