Rated 1 out of 5 stars

Firefox23 To we ask also correspondence.

Good while needs some polish Rated 3 out of 5 stars

1) It frequently places itself at the end of "statusbar" icons regardless of user customization
2) Unfortunately here is no any integration nor with standard nor URL Tooltip generated tooltips
3) No appearance customization
4) writen by previous reviewer

Anyway 4 stars (but one in credit)

upd: credit star cleared

Good and Working (up to nightly[11]), but ... Rated 4 out of 5 stars

It works, but only on static links. Any links inserted via JavaScript are ignored. This is caused by the way you insert your listener.
see https://developer.mozilla.org/en/XPCOM_Interface_Reference/nsIXULBrowserWindow#setOverLink%28%29
for a better way to get the link the mouse is over.