Good, but annoying Rated 3 out of 5 stars
Altogether, this is really useful while developing extensions, as it helps spotting memory leaks.
But the many windows it opens, and mostly the lack of any usable information (I know sometimes the source cannot be tracked) is simply annoying (especially while browsing).
So it should have another sort of notification method and/or a way to filter from what source I want to get notifications (XUL/(chrome-)URLs) (blacklist/whitelist).
Despite all this I suggest this to anyone who is developing extension(s) or happy with closing many many windows repeatadly. So keep up the good work, and thanks!