Rated 3 out of 5 stars
This addon is useful for finding leaks, but it can be very difficult to differentiate real leaks from "fake" ones.
For example any time I close a tab in Firefox 3.0 RC3 I get about 15 popups telling me that "[Window]" has leaked followed shortly after telling me that all leaks have been "reclaimed". Net result is 30 pop-up windows for 0 leaks.
It would be much better if the add-on could differentiate permanent leaks, from temporary ones.
That said if you are trying to test your extension and have nothing else installed in Firefox, this extension is useful.