This is really simple idea on how to get better feedback about your service: make a public feedback page and allow your users vote for others' suggestions.
You can even create a standalone service that will offer consumers this kind of feedback pages via open API.
I thought to write more clarifications and evidences that this idea is viable and good, but then decided to keep this up to you. Hope the idea is clear. But if you have any questions or you see some drawbacks - you are welcome to the comments :)!