I like AoO's personally. I think it makes a tough decision when you need to move through a threatened square, which is what makes the game interesting to me.
Indeed. Concept's been around forever, both in the rules and as house rules, to compensate for the alternating turns in the initiative system. 3E did a pretty great service in codifying the whole thing. The only way I could imagine 4E removing it would be if they overhauled the initiative system, and I don't know if that's very likely.