I just re-watched the E3 teaser and about the foliage; Has it occured to anyone that perhaps, the E3 teaser seems to have a denser foliage due to the fact that it's a controled cut-scene with very limited scale? In the gameplay sequence, you see Nate in action platforming in a very wide open area. Even the areas that seem off area, turn out to be actual places where you can go and explore. Rewind back to the E3 teaser and we have a scene, which probably received lots of polish to make it into the teaser that was revealed. Limited scale, huge focus on Nate close-up, one light-source and a slow pan showing the dense foliage.
I don't think it takes much effort into imagening that a very controlled scene, even at 60fps, gives a lot more scope to turn up the bar on everything, compared to a gameplay extract of 15 minutes that covers 1% of the entire game. We've all played heaps of games here, and even in the most impressive games, we rarely see a game that is consistent at its very best at all times. There will always be scenes and parts that get more polish or impress more than others. Uncharted 2, for instance, I think the generally some of the best moments are to be found in the later stages of the game (the Himalaya village). Same goes for KZ2 where the level on the moving train is extremely impressive.