Outside of the ever increasing scope, I think the most noticeable improvement is model detail. Even with the Warthog comparison, you can see that handles, buttons, bumps aren't just textures anymore.
Also, the part in the Vidoc showing fully modeled nuts and bolts on a wall, their "nose-hair geometry" is something I haven't seen in many/any games.
Also, the part in the Vidoc showing fully modeled nuts and bolts on a wall, their "nose-hair geometry" is something I haven't seen in many/any games.