I started Uncharted last Monday and finished it yesterday, I played 2-3 hours a day during 4 days to get through, played it on easy, so I guess I needed about 10 hours (as casual gamer). It was really good, I would rate it a 8.5/10, sometimes the shooting parts annoyed me a bit, as it felt like the same over and over again, I preferred the jumping and climbing parts.

Now I will wait until Uncharted 3 gets released, and then play the 2nd one