Me and my wife are working together on our new app (http://alephz.com). It's very early stage, and it's really just a side project for now, but I can see it's going well. I think the secret is to have a very clear separation of roles. For example, in our project I'm doing the technical stuff, and she writes the questions, and moderates the community.

Also, I think it's good for our relationship because we share the same hobby. I don't know how it's going to be when working together on something that isn't a side project, but a day job.