It does what it claims fine, no problem there... But 1st I'd like to be able to keep that window open while operating with the page - now pretty much wherever I click it closes.
2nd issue I have is with my small netbook - on this particular machine with fairly low resolution screen (1024x600) I tend to keep everything I don't specially want to keep quickly accessible from toolbar hidden, so I tried to pin the Netmon button to the overwflow menu, but when opened from there the window was way too narrow to be of any comfortable use. It would be nice if it opened just as wide from there as from toolbar.

All-in-all a good add-on - my complaints are very small.