Just finished the game, probably took about 3 days, playing 6 hours a day (hey, it's the holidays, I need to keep myself busy somehow
). It was superb, they definately mixed it up enough to keep you interested throughout the whole game, as soon as you start thinking "Hmm, this is getting a bit repetitive", they stick you in a vehicle or give you a new weapon to play with.
Warning: Spoilers about what isn't in the game, I doubt it's going to ruin anything for you though.
Unfortunately, the only niggles I had was that although there were a few areas where you got sniped, you never got to do any sniping yourself. I also noticed that several things that appeared in the pre-release videos never happened to me in the game, actually, I'll take that one step further, look in any 2003 video and you'll be hard-pressed to find something that actually made it into the game. Most notably is the 'Docks' scene, lots of videos showed this scene where Freeman picked up a crowbar and walked along the pier hacking away at zombies. I also noticed Alyx changed in appearance a lot, her face remained the same, but fortunately they changed her clothes from some weird body-suit thing and a green jacket to what appears in the game, a good change IMHO though.
I don't know if they changed it because of the code-stealing thing or if they just thought it didn't fit into the storyline, but it is odd to see that famous Dock scene gone.
There's also the very impressive video of Dr Kleiners lab (which seems to have been slightly redesigned as well) where Alyx is talking to you and acting very worried before handing you the SMG and a Strider comes crashing through the wall. I was actually waiting for that scene as well, just so I could hear Alyx say "Gordon, snap out of it, you're staring at me again." once more. Even more interestingly, there is a sewer-type scene in one video where you and Alyx are pinned against a fence and you see an enemy soldier getting up to shoot you before it's picked up by a glowing blue tentacle and pulled into the water, I believe it was in the 2003 demo video with the Dock scene, both were vacant from the final release.
I'm hardly going to call Half-Life 2 a bad game because some of the areas that were in the demo videos weren't in the final game. Without them, the game was still awesome, I just find it interesting that they were removed... and somewhat disappointing.
P.S. The ending rocks, definitely as trippy as the original's ending!
"Computers are useless, they can only give you answers." 