[nicw]

One thing I would add to this:

Goes out in person(!) and talks to customers.

It's very easy to add new features to products, but until you sit down with a customer, listen to them, and watch them use your product you won't have a clear understanding of their needs. Good product managers realize they are very close to a product and need to constantly take a step back.

If you're skeptical, sign up for a UserTesting.com account and watch people navigate your site. You'll be surprised.