Rated 4 out of 5 stars

Oh, one problem — the area where the "FLV MP4 3GP" etc. shows up, it blocks part of the description box, the part where it shows how many likes and dislikes the vid has.

This review is for a previous version of the add-on (1.5.4).  This user has other reviews of this add-on.

Temporary fix

Hello! I've made a temporary fix to this problem. Would you like to test it?
http://inf.ufrgs.br/~vbuaraujo/foo/good-old-youtube-downloader-1.5.6.xpi
I'm still not sure where exactly the download link box should go. What do you think? (I have put it to the right of the view counter for now because it was easier to program... :-P)

EDIT: Version 1.5.6 released (fixes this and the HD problem):
https://addons.mozilla.org/en-US/firefox/addon/good-old-youtube-downloader/versions/