After a slightly slow start, the game keeps you at the edge of your seat right up until the finale, which came too soon.
Half-Life: Episode 1 is a lot like one of these serials. The episode starts with some "missing footage" from the end of Half-Life 2 and then ends with a bang. What happens to Freeman? Stay tuned for the next episode in the series, where they will likely show us some more "missing footage". The technique is starting to get a little old valve.
In terms of game play, the game included some almost characteristically not Half-Life sort of things. At one point in the game you are forced to spot targets with your flashlight for Alyx to fire upon (or you could run your ammunition down to nothing). Another sequence has you reprogramming rollermines to attack combine, and yet another sequence has you escorting civilians to safety. And we can't forget how many times we are required to find the power box to activate the lights and doors (reminds me of Aliens versus Predator).
The graphics are starting to show a little bit of age, but fortunately a lot of new effects were added to the game to really spruce things up a bit. The fade in effect used during the opening scene as well as the looming tower in the distance are all memorable effects.
The sound was top notch, and in this category the voice acting was also very excellent. If script can be included, it would go here as well. The developers spent a lot of time trying to give Alyx personality, and they did an excellent job. At one point during the game a floor collapses sending you to the next floor down loaded with zombies. You run out of the room, break a door open and then go back up to see Alyx waiting for you. Her comment "You took the scenic route." is just an example of the comments that she makes from time to time.
Value is tough. The game was meant to be an episode, and therefore short. But no one ever worked out how exactly short your money is worth so to come up with a number, I tried to work out how long it took me to get through the game opposed to another of an equal value.
My first time through took me roughly 4 and a half hours. My second time roughly 3 (yes, it can be that short if you know where you are going). I always felt 1st person shooters could be longer and get more involved, this one was meant to be short, but it was just too short. I use the system cost/2 to determine length and then take that ratio. $20/2 = 10 hours. This game advertised 6. There is also little replay value, so it hurts this even more. Not to mention there is no extended death match option.
In all this is an excellent addition to the Half-Life 2 universe and I highly recommend it for anyone who wants a solid single player experience that they can easily beat in a sitting. The new effects (and enemies, I won't spoil) will sure to be used in the modification community.