According to this Kotaku report, the latest issue of GamePro contains new screens and information on upcoming Ensemble RTS, Halo Wars.
Apparently play's been speeded up to breakneck, and the only provision you have to worry about is "supplies". There's a partial list of units in the issue as well. Below:
Cobras (anti-vehicle artillery)
Wolverines (anti-aircraft vehicle)
Cyclops (enormous UNSC mech unit)
Vultures (mysterious, enormous vehicle)
Covenant Forces (not all units revealed)
Remember the game's not out till next year now. Hopefully the mag will be scanned in the next couple of days.