You are lucky that morons don't spare some time to insult you, but you are right that it's a problem that users that dislike your product just forget it instead of writing a report.
Have you tried showing it to friends or neighbours? It's important that you sit them in front of the computer and go back a few yards and look how they use the app without your feedback. Don't give them instructions, just see how they use it, where they get stuck, what they wish they can do.
Later they will lie and tell you the product is fantastic!!! Just hear the lies, smile, wave and thanks them. You are not interested in their oral feedback, just to see them using your product. (Some sugestions and wishes may be useful too.)