I absolutely love these stunning visuals, but a couple things strike me as odd. First, the Gravemind, while they're amazingly more grotesque, they don't seem as large as I had preciously imagined. Seeing John being dragged by their tentacles through that hall made me think that Gravemind was relatively contained. The original cinematic had the entire bottom surface of that dungeon and possibly the adjoining halls filled with Flood biomass. Seems like they're trying to give the impression that Gravemind is a much more contained and rather mobile being. With that being said, however, I totally love the new detail on their face. It just looks like what the Flood would be if it wasn't such a random mass of flesh but instead a brilliantly choreographed composition. Needs that stinky breath though.
The other thing is the camera set up. There are very few close-ups. Seems less personal. It just doesn't have the same emotional punch that the original cinematic did. I don't get the feeling that I'm supposed to emphasize with these characters. Only that I'm supposed to stay focused on stopping the key from tuuuurrrnnnniiinnngggggg.