The landscape is MASSIVE, and its completely free roaming, go where you want, blow up what you want. There is a constant fog, which is obviously covering pop up, and this can be a problem with the sniper, as you can see where your target is, (A yellow circle), but due to pop up you can't shoot them as they don't appear at this range.
The AI is fairly good, but you can sneek up behind it and it won't notice till you touch it.
The vehicles are great, you can get helicopters, tanks, jeeps, sports car and trucks. All of which are great to drive. Quite a few have extra turrets for allies and some you can control a weapon yourself, like a tank of helicopter.
The cream on the cake, The Merchant of Menace. AKA The Mafia. Wherever you are (Unless your near a radar jammer) You can order supplies, vehicles and airstrikes for a price. However you cant order tanks or heavy vehicles.
Aloong with capturing the deck of cards (generals, scientists and soldiers from North Korea), you can accept contracts from the Allies, the Chinese, the South Koreans and the Mafia in return for intelligence and cash. They are great fun, and you usually get free supplies/airstrikes/vehicles with them.
All in all a superb game.