The terrain in and of itself is a huge step forward. No more wide open, flight sim style outdoor, or cramped city streets - there is a LOT of useable cover, and a lot of game features that help you use it (if you haven't already, crouch (shift) behind a fallen log. Hit the right mouse button to raise yourself up and aim over the log. If you look at people crouched - they are very low when not aiming - cool stuff.)