One of the best things is being able to cause others to go to war, without going to war yourself. And the best thing about that... is that the AI uses that option. I was sitting there on my peaceful throne, not threatening everyone, being on bad terms with only two of the like 10 civs I was competing with, then BAM, Cyrus, who I had I think "Pleased" relations with at the time suddenly declares war on me. I guess someone paid him enough to do so.