Comment on What have you Googled today? by Ishetalia
THe only differences I know of are the graphical upgrades and that it's a new alien race for the baddies.
Aww, I was really hoping there was more, but judging from the screenshots even a lot of the screenshots look strikingly similar to Halo 3 
There might be more, that's just what I've heard though. I think since it's 343 and not Bungie doing the latest entry, they didn't want to startle fans too much.