Bug report window closes when main app closes
This may seem like the natural thing to do, but often when reporting on a bug, one may need to close the app and restart it in order to determine the minimal steps to reproduce the bug. If closing the app also closes the bug report window, then any notes already written there are lost, and the bug report window needs to be reopened and all previous information re-entered.
For instance, if the bug report window were opened in a separate process, then it could remain open while the main app is restarted. Alternatively, if the bug report form were opened in a web browser, then it would not be dependent on the main app's process.
Another alternative would be to automatically save the state of the bug report window when closing the main app, allowing the user to restore it easily/automatically. This could be done in a similar fashion to the 'automatically save drafts' feature in most email (and some forums) software/webapps.
Finally, at the very least, as a stop-gap measure, if the above suggestions would require too much time, it would be a good band-aid feature if the app warned the user if they have already filled out some information in a bug report. Perhaps allow them to copy the entire contents into the clipboard with a single button, so it can easily be pasted into another text app to save it for later. At least then no significant work will be lost.