Ooh, I agree with this. The idea of "we're more alike than we realize" is very powerful.

I also think that it's important to show the hate, even in an established relationship fic. For example, in Fab's Misericorde, even though they were in a relationship, we see the prior hate through Harry's eyes. Without the acknowlegment of the conflict, established relationship fic in this pairing seems ridiculous.

Show the hate; show the realization of common ground; focus on the tension as they try to bring the two into harmony.