Took almost exactly four hours for me to finish...while it is a bit short overall, the fact that it's so densely filled with scripted sequences, dialogue, gorgeous maps, puzzles, and good combat makes it worthwhile. Most of the game feels like the 'fun bits'...the payoffs which in other games you get after half an hour of slogging through monotonous corridors shooting the same enemies over and over again come almost constantly and are integrated into the overall gameplay and keep things rewarding. In the GameInformer preview, they talk about the focus of Ep1 as being 'single-player co-op', and they really pulled it off well. Alyx is actually useful as an ally, the acting (voice and animation) are exceptionally well done, and her constant presence is well-executed as a way to give you regular feedback. I've spent $18 far, far worse than this.