Gameplay Features
Deformable Environment
The most noticeable difference is the interacting environment. In C&C2, there is an interactive terrain, which will affect the game play greatly. Normally, RTS games are 2 dimensional with a trace of a 3rd dimension in the form of fliers that don't really follow the laws of physics. C&C2 will have a sort of the pseudo physics seen in a first person shooter game. Grenades will bounce differently depending on the surface. Bridges can be blown up, but now they crush whatever is underneath them instead of just dissipating. The terrain itself is also interactive with the unit's fire or movement. Like the original C&C, you can burn down trees. But unlike the original C&C, you can now walk through where the tree was. Westwood also includes bodies of water, like every other RTS game out there. Unlike the competition though, the water will freeze over or melt depending on the climate. On top of this, if you're on thin ice and move over it with a heavy unit, that heavy unit will be introduced to a cold bath.

Looks like a mecha, but this isn't a mecha game.
Experience Counts
The unit interactions are huge too. Westwood has always been the most "realistic" of games when it comes to fighting in that the units have bad aim sometimes. They've somewhat improved on this in that now units can gain experience if they've been in heavy combat and become veterans. These veterans have a much better AI and supposedly have a much lower chance of missing their target. My only question is if you start shooting your own guys for target practice, is your new smart unit going to be better than the old stupid units? If so, Westwood might be in for some flames because this may create imbalance; imagine shooting up your own units for experience and then repairing them. Besides the addition of unit experience, Westwood plans on incorporating more realistic shrapnel that hurts surrounding units at a certain trajectory instead of a radius in most other games.