A great introduction to a new episodic trilogy. Well worth 20 dollars!
Gameplay: Episode One plays noticiably different from the original Half-life 2. This is obviously because Alyx Vance is with you 100% of the time. Luckily, she's not an annoyance. Alyx knows what to do in combat and will not repeat any dialogue you've heard before. Too bad she becomes a Combine soldier and Barney has to take her out... (just kidding)
Several new gameplay elements have been added, from Combine Zombies to re-programmable rollermines just to name few. This game is awesome fun from start finish.
Graphics: Episode One benefits from an enhanced Source engine which features HDR lighting, more detailed textures, and better animation. High Dynamic Range lighting in this game is just beautiful and does not have as much as a performance impact as Lost Coast did. You'll notice that characters are more detailed, in terms of textures and animation. Just watch Alyx struggle with a Zombie in close quarters combat. She knows kung-fu!
Sound: All major voice actors are back voicing their characters and like Half-life 2, the acting is top-notch.
Conclusion: Every HL2 fan should get this game. If you're worried about length, you could hold out until late 2007 when all three episodes are released together for around $50. Still, this game is well worth $20!