It definatly is going to be shorter game than Halo 3, probably around two hours shorter at minimum from what I saw, granted he was playing on easy mode which is a cake-walk in terms of difficulty.
This guy's gameplay is an epic fail... First he gets completely lost. Then later on he frontally assaults everyone and everything, even multiple Wraith tanks and plasma cannons... then he fails to notice that he could nick a Wraith or two for himself...
Eh, if all those Halo bashers you see on the net play the game like this then I've just had it all explained to me.
Also, you could at least double the gameplay length, and there's about 23-24 9-minute parts including cinematics, so it's more like an 8-10 hour game IMHO.
Overall I thought the production values where superior to Halo, and it just looked like a much more cohesive single-player experiance.
The nighttime city streets with all the smoke and neon lights look simply amazing. I think I'll have to buy this pretty soon, ironicaly these leaks are what convinced me
Although I don't really get the difference between playing as an ODST and as Master Chief, both can jump pretty big, kick Brutes in the face and so on. Although I have to admit that the Hunters are really big and scary from this perspective.