This is specifically about combat and AI in combat. Not about generaly smarter AI. There is a thread for that here: http://www.gamesas.com/index.php?/topic/1166835-skyrims-ai/
As far as Ive ever been able to tell(Ive not done any testing) in Oblivion or Fallout monster hate is really only based on damage. Which is perfectly fine with Oblivion because it was made without real followers and you were almost always by yourself anyway, and in the event that you have a companion mod and YOU want to wade in with heavy armor swinging a big sword youd be doing most of the damage anyway. But with Fallout its a little different. Im going off mostly New Vegas here because even with mods I never used companions in Fallout 3. Im using Veronica, and shes wearing Power Armour. She will run in and literally start knocking heads off but usually everything still runs at ME hiding in the shadows and not the crazy happy psycho with a shotgun for a hand. Its just... kind of immersion breaking and it really makes using companions lame.
Back on Oblivion YOU can tank fine as a heavy melee, but what about Mages or Thieves that dont want that attention? What if you want to use a big angry Nord as a companion in Skyrim(Im going off the assumption there may be vanilla companions in Skyrim) and have him sort of like, tank? Or you conjure a REALLY BIG ANGRY DAEDRA as a Mage and want it to soak up hits but not be stuck not being able to toss in some Fireballs, and thus be stuck standing around summoning more REALLY BIG ANGRY DAEDRAs when your REALLY BIG ANGRY DAEDRA dies, because youd just pull hate off the REALLY BIG ANGRY DAEDRA by doing much else?
EDIT: Not only would this allow people to play a more tanky role, but it would also make support or healer characters somewhat more viable and fun to play.
Even in the event that aggro stays the same there are NPC combat AI issues that I dont really have faith in Bethesda fixing. At most maybe theyve tuned NPC AI to NOT shoot you and other friendlies in the back, but thats not enough IMO. Positioning is a big deal when it comes to fights with more than just You vs. 1 NPC. IDK about you guys but I HATED how NPCs would all just make a strait beline and bunch up in one spot on what theyre attacking, like trying to help a Guard only to have another Guard run right in front of you(and with me it usually results in an angry Guard with an arrow sticking out of his backside).
Dont bother with the "New game engine" crap response, it holds no water. Not only do we NOT know how the new engine differs(or if its even any better), but it wouldnt make any difference if the Devs dont think of or want to change this kind of thing.
Personally I would like a little more flavor for combat, like say... backstabs. You can argue that because an NPC already cant block your attack if youre behind him that can be considered a "Backstab Bonus", but I disagree. Easiest thing to do is just slap a multiplier on and forget about it(stacking with sneak attacks as a reward for the trouble of sneaking up to melee). I dont think its the best solution but its a lot better than not having any kind of bonus for being smarter and the somewhat more effort to position yourself properly in combat(kind of like six). I encourage people to suggest other kinds of bonuses or Perks for combat positioning because I know theres some ideas out there(Deadly Reflex) and Im sure there are better solutions than mine.
The only reason I really bring up positioning is NPC AI though. I would like to see NPCs flank. Each other and the PC. I would like, if I am playing a S&S heavy armour wearer, my Rogueish follower to circle around and flank monsters without me needing to abuse poor AI. I dont mean the little side-shuffle marksmen NPCs do in Oblivion, but really try and get behind(or on to elevations) so they dont hit me with a fireball when I sidestep just an inch. The coolest thing would also being able to send in said Rogue to get a sneak attack off on a patrol or watchman, or NPCs to have more combat personality in general. I can understand this may create a problem with terrain pathing but I should hope under a new engine youve fixed this a little bit.
Oh, and Turtles. Why Turtles? Well ever since Id seen the weapon chart with dual wielding shields(which I still think is just a joke btw) it made me think that maybe we CAN play a very defensive character, and use followers(including summons) as a source of damage. This was why I brought up the change of Aggro from being based on just damage, because a defensive character would need another way to attract attention than abusing AI on corners or causing the highest damage.