If warfare is not a substantial part of the game...
See, that is where it is very hard to draw the line. I think NOW war is a substantial part of the game, while before it was almost the ONLY part of the game. While you were discussing I was playing my newest Germany game; neighbour Babylon. Huge trading partner, huge wonder spammer, so based in previous speculations/some analysis, Babylon would have been my "safe border", right...?
Wrong! He slowly but steadily accumulated power, showing his friendly face, keeping most routes with me as I was doing with him... building up his army. When it was ready, he launched a surprise attack. Granted, was not turn 50 as some miss, but was it better? Hell yes. I am still fighting an even war of attrition, slowly gaining the upper hand. So even if he was a major trading partner, getting a lot of money from it, even if he was going tall, even if he is not usually the warmonger... he came for me. That is Emperor.
Somebody mentioned horror stories about the BNW Iroquois. Indeed, the horror. I had them my very first BNW game; they completely dominated their entire continent, knocking out two civs, and when I met them, it was too late. I tried, but he made me pay with disaster my attempts at the WC and with inciting revolution. Also Emperor.
Point is, the line is blurry. While some think that the "substantial" part of war was reached with G&K, others think that it was finally reached only now. What cannot be denied, I think, is that at least now the AI tries to compete in all arenas, and what I see is that they usually compete in where they should be stronger IN THE LONG RUN, and not only in the beginning. I have to say that I ALWAYS play Random Personalities (to me, there is no strategy in knowing your opponent's behaviour from memory but in adapting to an unknown one), so I wonder if that could have something to do in my, so far, very good experience with BNW?