When you submit a bug report, you're certainly helping--but you're helping other users and yourself. You're not helping the developer (if they hit the bug in their use of the software, they'd just fix it).

I'd have to disagree with you there Mr L. Non-descript bug reports are useless of course but well-constructed, up-to-date bug reports are surely of use to a developer who cares about his project but doesn't have time to thoroughly test it- which is the case for most FLOSS devs. Just because a dev hasn't spotted a flaw yet in their usage of their software doesn't mean its not a potential showstopper for other users of that app.