It would depend largely on what our exact differences were. Some would be dealbreakers, some not so much. If I can see where she is coming from, and believe that a rational person could have that point of view, I don't see an issue. My SO of four years and I are quite close politically in most ways, though, and anyone I've been involved with in the past has either been close to me politically, or far-apart but not particularly political as a person so it wasn't an issue.

Definitely not as important as religion. I don't think I'd be compatible with anyone who wasn't agnostic. It sounds bad, and I'm not trying to be an edgelord, but if I'm being completely honest, I see "I don't know" is the correct answer to religion to the point where I have trouble sympathising with religious people. There's a certain fundamental respect that just isn't there. I don't talk about it, because it's pointless, and I can still get along with them fine, but in the back of my head there's always "wow, this person believes in the bible and shit"