Um, lots! A simple cutscene isn't indicative of what you'll get from the game. The Halo 3 showing may have used 100% of system resources to show that scene, and the moment real complex scenes are involved they'll need to cut back on quality. I'm sure you've indicated as much on PS3 showreels(?). We don't know how this engine performs with a couple dozen people battling in a smashed up city, say (or whatever the battleground will be). eg. If Master Chief looked so good because they blew most of the GPUs poly budget on him, the moment more characters and scenery polys are needed they'll need to cut back. Or adding 4xAA my have more of an impact the moment you add a lot more geometry crossing the tile borders. Unless Halo 3 is played in sparse deserts with only one character running around, the demands made of the system in that trailer are not going to be anywhere near what the game will have, and so won't be indicative of in-game graphics unless that trailer was using only, say, 50% or less of system resources.