Half Life 2 Episode One might just be more exciting then it's full length counter-part.
Pros: Better AI is a huge plus. More of a Half Life 1 feel to the combat. Episode 1 uses the Combine's ability to repel from walls and such alot more and to better effect. Alyx is the smartest AI helper to ever appear in a video game.... so far I haven't had to go looking for her once, even Oblivion makes you back track to find NPCs following you. The scenes are more intense, especially one key scene in the begining involving you, dog, and a van. It's like with HL2 the designers knew what they wanted, and with episode one thats finally realized. Small things like watching Dr. Kliner tell people to have sex on TV. Small things, that make you feel like you are Gordon Freeman, humanities last hope. The lighting effects are.... the best. I haven't seen anything like it before. The red swirl of clouds above the citadel are very impressive. The game is totally immersive, and the ideas and themes are the most original to be placed in a video game to date (in my opinion). The enemies are awesome as always, with the addition of Zombine Soldiers. The Zombine have a nasty habbit of busting out a grenade and running at you with it. Grabbing the grenade out of thier hand with the Gravity gun can be very fun. Another interesting twist with the AI is that, you'll find enemies fight one another alot more frequently. In HL2, you really didn't see (atleast that I remember) zombies fighting combine, combine fighting head crabs, ant lions fighting zombies, and so on. You'll also find alot more ant lions. All and all, shooter fans don't want to miss this game. It's fantastic and takes HL2, no, gaming in a new direction.
Cons: Well, there aren'tany true cons. My only gripe, when I first downloaded the game and then went to play it... The loading screen would get 3/4 of the way and stop/lock up. Steam support was no help AT ALL. So, I looked on the GameSpot forums and some dude had the answer. If your having this problem, and have a ATI graphics card (the problem is only with ATI I think) here's what you do: Desktop users, download new driver from ATI. Laptop users (like me) download the DESKTOP driver for your card from ATI.com Then search google for DHmodtool. Follow the mod tools instructions... it'll convert the desktop driver to a mobile driver, and you'll be playing Episode one in a matter of 15 mins.
Final Word: You can never go wrong with Half Life... and Episode 1 prooves that even further, even though it's short (it's supposed to be! So stop complaining people). I'm excited to play Episodes 2 and 3. Many have called the episode "Half Life 3".... hate to tell you kids but, the episodes and Half Life 3 are 2 totally different things! We'll all see, soon.