The targeting can get annoying. There were plenty of times when I was trying to point to one specific enemy, but he would keep aiming for someone else. The OT misses downed enemies fairly often as well, which also sucks. But overall it's manageable. I don't think I ever had him attacking the air or anything, he was always going for someone. (if that did happen, I don't remember it anyway)
Also, I don't like mission mode so far. You earn points during each mission, which makes your ninja and weapon level up (like an RPG), which keeps unlocking more attacks and making them stronger and such. But that's just really annoying because you're basically stuck with a gimped character until you grind your way to max rank. There are also random 'contracts' in every mission, and completing them earns more points (stuff like do an izuna drop, do a UT, do a steel on bone, etc.), but those can be kinda annoying too because activating a steel on bone with the slide combo (which I haven't unlocked yet) is left to random chance. And the missions are too long.
I also don't like how they seem to be designed around co-op. But at least you can choose to play solo, unlike Sigma 2. I guess it remains to be seen if the later missions are even possible to complete by yourself.
