I'm co-founding with someone with that dynamic (I'm handling product, she's handling business). Luckily we know and trust each other from way back, so tension isn't a problem, but there has been an interesting power dynamic - originally I was more in the driver's seat, since all we were doing was product development and there was no real business decision to make. Now that we're actually selling to customers (and investors), she's more in control of things, ie is more qualified to decide what features are important for business reasons.