At HaloWars.com there's a new monthly update about Halo Wars, written by Thunder. It's mostly about the game's AI:

Ultimately, the philosophy that we’ve had at Ensemble Studios is that the most fun games are when you think you might lose but don’t. The CPAI should attempt to provide the player with this challenge in each game. We want to set the difficulty levels to where most players will find a challenge, but there will be a level that can beat them if they start making mistakes.

Check out the update in the Halo Wars forum.