A full list of G-Man sightings in Half-Life 2. I can't believe I've missed so many; I think I've seen him twice.

Update 19:00 - I finished the game. Spoilers inside.

The ending was quite abrupt, but when I think about it, a "last guy" is so inappropriate. It'd make the game feel like a game. The best thing about it was that it was so immersive. No cut scenes and load times broken up to keep them to as short as possible. I look forward to the inevitable Gearbox expansions and Half-Life 3.

The super gravity gun and the last chapter or two of the game were absolutely amazing. The game absolutely got better as it went on.

Next step, see how far I can get in difficult, and wait for the SDK release.