No new guns, enemies or multiplayer additions. Valve brings the same old great gameplay, but forgets the special sauce.
After spending $14 (it's 20 on valve's pay site) for the new expansion I was ready for a little more than the 3 or so hours of game play that I received. Valve did not bring anything special to the game play imo.
The AI for Alex was great, and they definitely tightened her character up w/ quirky remarks, and a generally good sense of humor. She seemed a bit awestruck with Gordon's skill at dispatching the alien hordes, but I let it slide.
The same AI that made Alex so believable, and endearing seemed to be lost on the other npc civilians. I was forced to restart several times in the stage where you have to run civilians between the two train stations. Several times they would get stuck, or run back to get a combine solider that fired at them from several yards away. If I was a civilians I'd be keeping my head down, and running as fast as possible, not trying to take a combine shotgun in the head because he suddenly spawned close by.
The game was standard HL2 fare which isn't bad, but a new gun, some new enemies (combine zombies c'mon that's a slight cop out. they are faster, and suicide bomb you with grenades) maybe even a new MP level or something would have just helped the game out a bit.
In all the game play was great and the audio as always was amazing, but the quickness with which it is over, and the next cliffhanger we are left with left an empty feeling in my pocket.
If you love HL2, and must know now what happened at the end of the first storyline get the game (but look around at retailers because 14 bux is better than the 20 they are charging on steam). I'm figuring in the next 6 months when Episode 2 comes out episode one will be 5 bux or so. Which imo would be a good value for this type of episodic content.