Looks like they made the combat more frantic... hopefully it doesn't remove the strategy of combat that the first had. Other then that it all looks good. Love that you can be under water now!
To those complaining that it looks too much like the original, what do you expect? It takes place in the same world that the original did... and the original did not look so bad that they need to overhaul the graphics.
I didn't see a "frame rate drop", Too me it looked like they slowed it down to add more drama to the water bursting through the glass... its a trailer not actual on hands gameplay footage. Alot of it is staged to show off key things.