Personally, I'm a little bit on the fence about it. I don't dislike it, as much as I'm ambivalent about it. It's most likely because we're only playing a third of a game right now, but to me the Ideology system feels irrelevant, I guess. The way I view the ideologies it seems like good is all about influence victory, neutral is about tourism (if I remember right, I don't have the game in front of me), and evil about conquest.
I've tried each of the three branches, and don't have a particular preference. From a gameplay perspective right now it's hard not to choose evil every time considering the only victory condition is conquest, so that may skew my opinion of the ideology tree.
But anyways, enough about me: what do you guys think of ideology as a concept and its implementation?