Generally, investors are wary of married couples, in that they've been burned before. So we need to be very cognizant of the way we act around each other to ensure they get the most positive impression. If you read accounts of the flickr cofounders, you'll also get anecdotal evidence (that I've never experienced) that some investors are assholes and don't take women seriously.
We have complementing skillsets, which is perfect on the work side of it.
On the relationship side of it, I have no idea how people do startups that have significant others _not_ involved. Not only do we spend the vast majority of our time on the project, but we talk about it when we aren't working on it. How could an uninvolved party tolerate that?