Fuolornis Fire Dragon posted a link in the forum over at HBO about a post Butcher made regarding Halo's AI. Specifically, there were questions asked about whether or not you'd be able to issue orders to the other marines in the game. According to Butcher, this really isn't necessary:

Anywhere that you'd like to tell the marines to move up or fall back, it's more effective to lay down the lead on your foes than it would be to fumble with buttons on the controller and issue orders. I'm pretty sure you'll agree once you play the game.

It's a short read, but a good one.