How is it being a product manager (PM) for the blade/piece of product that you develop?

I might have the opportunity to be a PM and a developer for the product I've been working on for the past 3 months. I feel like I have a pretty good grasp of the product, but definitely don't know all the customer needs/wants (which I assume will come with more knowledge/experience with the position). Is there anything I should be wary of if I get the promotion? How much of a raise should I expect or ask for?