Also,
There are a few cool new maps. Thanks bustr!

The trees aren't nearly as sticky as they used to be, and they don't reach out and grab you. You can drive through the smaller trees and bushes. (Lemon trees = good; orange trees = bad.)
The clouds have been refined. They look really good and hardly affect frame rates.
There are now battleships with 16" guns (on some maps).
Trains and convoys run on some maps. I guess they affect rebuild times, but haven't seen anyone attacking them.