I don't like AOO's. Dealing with new or part-time players, they can't parse the rules. Dealing with some expert power gamers, they take a very long time mapping out moves to avoid all possible AOO's. I prefer rulesets (1E) that force you to stop moving when you contact an enemy - that's much clearer to part-time players.
Justin Bacon said:
1. Can someone hit me?
2. Did I just do something that provokes an AoO?
(1) Player may not know
a priori if someone can hit them. (Hidden, invisible, unarmed, armed with reach weapon, natural reach, etc.) Need to track exceptions for cover.
(2) There's a 100-odd list of cases that need to be memorized or tabulated for these "do somethings".
Justin Bacon said:
1. Can someone hit me right now?
2. Am I still going to move at least 5 feet this turn?
3. Will I have moved more than 5 feet this turn?
(3) See above.
(4) This is a forward-looking statement that some players have difficulty with. In other words, you need to mentally map out the entire future move before you can determine if starting the move stops the move and lets someone else act first (AOO).
(5) Then you also need to mentally track if any or all opponents have made AOO's earlier in the turn, against anyone, so as to be eligible to take AOO's. Then you need to know whether any have Combat Reflexes to act as an exception to that.
So when predicting AOO's you need to consider the past (enemies making AOO's in previous turn), the present (my action, position on map, all enemy positions on map, enemy weapons wielded, cover), and the future (entire movement I'm about to take), before knowing whether AOO's will occur. That's a lot, and a lot of the information is not available by just looking at the battlemap.
More generally, for part-time game players, the idea of it being "my turn" in a game and having it be invisibly interrupted by someone else getting an action is very unsettling and confusing.