How do I gauge interest in my startup concept?

I'm trying to rev up a startup with a couple of friends. We're all devs and we're just sort of throwing up code and ideas towards an MVP. We're doing a B2B SaaS thing that already has a pretty big market. We're just trying to iterate on existing products and beat them on price and style. We really know nothing about running a business or getting customers. Obviously we can't predict the future, but should we keep hacking at our MVP, or should try to find early adopters to help guide our features?