Episode One's truncated nature and paucity of variety undersells what should have been a vastly superior game.
Core to this bite-sized shooter is character development. Alyx accompanies you (Gordon) throughout the three hour journey, though she seemingly serves as a gameplay device armed with fistfuls of hints rather than being a meaningful addition to the story. She is an object of annoyance throughout, bumping you out her way in a most un-lady like manner as she strides down her pre-determined route. Her aptitude for continually perking up with: "Hey Gordon, why don't you try X or Y is a frustration too, since it's such an obvious gameplay mechanic that feels wholly unnatural to this ingenuous series.
Maybe I'm nit-picking, but the overall scope of Episode One is severely lacking. It doesn't feel as ingeniously weaved, it's too obviously forced and, parallel to the abridged length, it lacks necessary variety (they seem to run hand in hand: less game, less scope). Sure, you get to escort hapless allies outside during the final fight, but the ensuing gameplay is uncharacteristically formulaic.
Arsenal increments are ominously lacking too, though the visuals are improved through the use of HDR-Lighting. It's still a legitimately good looking game with the trademark facial animations heightening your sense of immersion. Though, coupled with the realistic physics, it's a shame Valve didn't feel more ambitious throughout the truncated adventure.
In saying this, it's more Half-Life 2, a commodity I'd be hard pressed to condemn. And, given the quality of its successor (Episode Two), you can write off Episode One as a bridge between Valve's more obviously inspired efforts.
At any rate, Half-Life fans will eagerly devour this, and so they should. It's another notch on Gordon Freeman's journey. Nonetheless, we are deserving of better.