Poor / not complete Rated 1 out of 5 stars
Its a great tool, but it didn't work with over 50.000 messages (that could be explained by our very slow responding imapserver)
1 major drawback is that this tool needs to make a copy to the trashcan which slows it down considerably.
Please file a bug...
Please file bug reports for the first issues at www.mozdev.org/bugs .
As for the first issue, this is not true - you can choose to erase completely rather than move to trash.