There are dealbreakers (same religion, no kids, etc.) and dealbreakers (K, he has to be tall, and really, really, cute, and I will never live in a weird state). I think the major ones need to be put out there very early on (ideally before scrabble and all the emotions that go with it) and the other ones are more 'wish list' and best kept to one's self. Personally, I would NEVER have lived in NJ, much less married a man with 3 young children, if you'd asked me - but I fell for the guy, so what are you gonna do? However, I have not - and will not - convert for him, nor would he ever ask me to (but I did get him to switch to my political party, so score one for me).
And I will add the following - flexibility and compromise in a long-term relationship are key. The children (when I met the King) were obviously being raised in his religion. I have some issues with some of the tenets of his religion and he & I strongly disagree, but I agreed to continue to raise the children as such and will do so. But if they ask me my opinion, I am honest - and the King is cool with that.