If it's okay for me to suggest an Allied AI improvement, I've been impressed here and there when they actively get behind cover and start shooting -- not so impressed that for no particular reason (even when I haven't moved) they then wander out into the open and all but say "HEY! SHOOT ME!" or into open ground for a Nerbelwefer to blow 'em up.
I loved NOLF, but the Half-Life marines and ninja assassins remain my favorite AIs. I've maybe experienced better technically, but those stick out in my mind as most memorable in single player.