This wasn't too well received by fans, mainly due to its length and the fact that it's all setup and no payoff. The concept of episodic gaming was quite new at the time. The low price now, and the fact that you can play Episode Two right after if you like, means these aren’t big problems. It’s not bad, but it’s also not great. Maybe it’s just because I’m comparing it to the legendary Half-Life 2, but something is lacking.
On the surface at least, there’s very little that's new here. Most levels feel like they might have been abandoned during HL2’s development, and then adjusted slightly for this Episode (though I’m not saying that’s actually the case). No new locations, just new areas of locations we’ve already been in. No new weapons. There’s hardly even any new assets. There’s one new enemy... But, that’s it.
This episode has a focus on Alyx, her character development, and teamwork with her. They succeeded at that, and her AI is a lot better than the normal friendly NPCs. Or at the very least, she isn’t a burden. Since she’s such a great character, it’s a welcome change to go through game alongside her. It also took a darker tone (and darker levels in the literal sense) than HL2, which was originally supposed to be a darker game, and they were probably trying to explore that a little with this episode. So there are new things here, there’s just not a lot of substance to it.
Still, its 3-4 hours of your time, and it leads into the fantastic Episode Two. It's a perfectly adequate game, it's just not a very adequate follow-up to Half-Life 2.