AI given a "move" waypoint do not move at a reasonable speed - they continue in tactical pace despite there being no threat.
AI, despite having been given waypoints to the contrary, will stop and hold a position if an enemy helicopter passes over, expending all of their ammunition, despite there being more serious threats to them.
AI, when under fire close to a building, do not attempt to seek cover but instead stand around the outside of the building, being shot.
AI, even when presented with an overcomeable enemy force, will often flee. This is usually through open country without cover.
AI is unnaturally accurate at shooting over long distances. If the player fires from one position and is spotted and so moves to another (entirely out of sight of the AI), as soon as he fires a single round from the new position, the enemy will engage straight back, usually scoring a kill shot within a single burst.
AI is remarkably dopey in CQB situations.
Friendly AI cannot detect hostile AI and players even if the player is looking straight at the threat through a scope.