Personally the AI was one of the strongest points in the game. It definately learned and adapted to my tactics. If I used a lot of melee, they'd try to. If I tried mostly stealth, they'd adapt that way too. Similarly they'd adapt to weapons that way and mix through the strategies I used.
If anything the weakness is that until you start using grenades and smart tactics, the AI won't try to flank or anything. It autoscales based on how good you are.
If a player or reviewer just blindly flies in and kills things with no thought, the AI will act stupid like in a normal FPS. If you're smart, conserve your shots and take cover for a 'zero damage approach' like people do in a game like Thief you'll see the AI act accordingly and be rather bright.
