Based off the beta I previewed:
1. The maps can be huge...kilometers across in either direction. They just haven't released any of them to the press. I edited one that was a good 2 km x 2 km (I don't have the patience for anything larger).
3. A realistic number of vehicles: tanks of multiple types for each side, jeeps, APCs, etc. The texutures for each just aren't done yet so they might look the same in screenshots (placeholders).
4. You can put in parked cars, plus destroyed or disabled vehicles. You can even put an empty humvee in a location and have an infantry squad try to reach it to drive out of the map. Hey, that gives me a scenario idea.
5. There are four grass textures and lots of trees, so foresty areas are possible. Again, they just haven't released maps in these areas yet. But I've edited some