PLEASE UPDATE Rated 1 out of 5 stars

no downloader add on is working now..please update..the only way to download now is using internet download manager to download hd mp4 & sd flv but no sd mp4 wch is wht i need desperately :(

This review is for a previous version of the add-on (1.4.4). 

It's probably an YouTube experiment you can disable by clearing the cookies for youtube.com. I've just tested both the extension and the Greasemonkey script in Firefox and other browsers: it still works for me.
<br>You can help me update the extension to make it work in this experimental interface by opening youtube.com in a tab, pressing Ctrl+Shift+K (or Firefox menu > Web Developer > Web Console), typing document.cookie in the console and pressing Enter. Copy the result and paste it in an email to deadline.support@gmail.com. You should do that before clearing the cookies. This helps me test the new interface. Thanks.