I get so many bug reports like "This sux and you have to fix it!!!!" and even when I wake up on the right side of the bed, there's nothing I can do with those.
A calm discussion of what the developer is trying to achieve, what they expect to happen, what actually happens, and how I can reproduce will get a quick response from me 100% of the time.
That said, when someone open sources something there isn an implicit "contract" between the developers and users. The users' feedback helps the developers and in return they get something valuable. It's more of a group effort rather than some one directional flow of power. I've seen projects where these relationships weren't properly managed or where one group didn't appreciate the other and the end result is always the same: dead projects.