I think his AI was vastly improved in this game making him a much more versitile ally than the last game.
My only gripe "which isnt really a gripe" is that his armor seems so blah, I mean he is supposed to be a ceremonial warrior of the covenant yet his armor is pretty much the plainest out of all the elites.
I understand that it is old since its been passed down for years but look at the Prophets elite guards in Halo 2, they were awesome in there armor, yet the Arbiter who is supposibly above these guys "if in image only" is rollin in the old trashcan armor set.
I just think that Bungie could have done alittle something more with it to make him alittle more distinct.