RTS fans will be glad to know that the Halo Wars official site was updated recently. Ensemble has been working hard, and they've let out some minor updates over time to prove that. Check the link below to see everything on Halo Wars.
http://www.halowars.com/default.aspx
It seems two new units have been revealed in the Halo Wars universe. The warthog, which I can only assume you've become familiar with, and the UNSC Firebase. As it stands, the warthog has multiple stages in which it can be deployed. The most basic leaving it without an M41 Light Anti-Aircraft Gun or a gauss cannon equipped. Recon patrol is the main focus for these warthogs. However, if you prefer a more deadly approach, you can upgrade and slap on the M41 or the gauss cannon. This will slow the vehicle down a bit, but you'll need a gun eventually.
The other unit, which might not be quite as familiar is the UNSC Firebase. This versatile unit can create those little Warthogs, so it's rather large. The Firebase acts as a tactical command center, and can supply both vehicle and infantry support to the battlefield. This is said to be a great advantage of the UNSC on the ground.
Opinion: While I'm looking forward to Halo Wars, I just haven't seen enough to prove to me that it will be a fantastic RTS on a console. This E3 will hopefully answer some of the many questions I have, and that's something to look forward to.
Ensemble updates every so often, so keep your eyes peeled for new information.