"It's not that difficult to make an enemy FPS "bot" have superb tactics, coordination, timing etc. Especially if the map is pre-known (which is usually the case). You can code the tactics and heuristics in. If you hear the player in position X, group A enemies head to position Y and group B head to position Z, and bye bye player."
I'd say the holy grail is to have the AI without pre-knowing the maps, and without having to hand-code the small details.