AI improvement over civ 5 vanilla?

I've played all civs except latest civ 5,finally i got pc capable of running it and will buy it in a week time.
I've heard/read a lot about AI in vanilla isn't quite well and up to the task,so is situation improved over 3 years?

A little, but not much. diplomacy is a little more involved, but combat strategy is not so good, especially on island maps with a navy.

Also, it seems to ignore going into debt during war, although does suffer from unhappiness (I saw a bunch of rebels appear in its lands once).

Maybe a bit in diplomacy and the economic side of things. There is at least some logic now in its diplomatic choices. Previously the AI seemed to behave completely at random - unpredictable sure, but also ineffectual. The military side of things hasn't noticeably improved. The AI still doesn't have a clue how to deal with 1upt or how to effectively use its ranged units. Pretty much any human player will crush the AI in combat even if on paper the AI has 2-3 times the military strength.