One thing though is that unless it was specifically made not to show us things, a lot of placeholders seem to have been used in the video...The grunts appeared to be from halo2 (exact I mean) but with the better normal map rendering system, the smg, the MC's arms. Also of note is the crappy contrail system in halo 3 currently...Can't wait till thats updated, like the contrails on the spiker look choppy and blocky...
You could see a lot of visual upgrades to halo 2 though, the plasma grenades in action look awesome!
apart from the things I've pointed out (even though its an alpha), the vidoc upped my anticipation for halo 3

What do you gyus think of it?