CS on Source (HL2) Engine is a bit more different, pace of the game feels different, which along with the rather smart new graphics and physics it adds a bit more spice to the tired game...........for all of 30mins. Half life 2 has no standard multiplayer at this point, only CS: Source. I've got HL2 pretty much fully pre-loaded onto my comp through Steam using the activation code I got with a Radeon 9800XT last year, as soon as HL2 comes out (16th) it'll be unlocked and ready to play.
I'm getting the Limited Edition Halo2 on launch day, and as soon as I get in from work I'll be playing it all night on Live. Almost tempted to book a day off
My gamertag is in my signature.