Disappointing.
The good:
Great idea by Valve to give us a teammate. Alyx is going to be with us the whole game. She has unlimited ammo and life, which is great. She is also tells joke sometimes, flirts with Gordon, etc. Great idea.
The graphics are improved, better than HL2. Valve added HDR, higher resolution textures. The game runs at a steady 60fps on my 7800GT, A64 3200, with all settings maxed out(4xAA,16xAF). Good eye candy.
Oh, and one more thing. The price.
The bad:
HL2's story.. well I think it's similiar to the TV show : LOST. No, the story is totally different, but the pacing, well, its' the same. The only difference is, for 7 months out of 12, we get a LOST episode (almost) every week. While we get a HL game once in 6 years, and an episode - according to valve - once every year.
The story didn't advance much in this episode...
also, the level design is pathetic. The first level was alright, we didn't have to use much firepower. But it got really repetative after a while ; you grab one of the energy balls, throw it into something mechanical, it starts working, you move forward. The 2nd level is even crappier. Doom3-ish, you just go ahea din the dark, shoot,kill,shoot,kill... bah.
The 3rd level(City17), is, although great.
Now, for 20bucks, you get a game with3-4 hours worthy gameplay. 20bucks, yeah, But come on. A game with no replay value, and only 4 hours? Thats very bad.
Overally i'm not too impressed. Gabe Newell also stated that it's not really HL2 E1 but HL3 E1. And if this is really Hl3, then im VERY disappointed.