It's cool but the filenaming is flawed. Rated 4 out of 5 stars

When there's a ":" in the page title for the youtube video it generates an invalid filename with some invisible invalid character. When the video title name ends with a "." the file extension is missing.
A smaller issue is that it can't always determine the filesize of the videos, which is a neat an unique feature BTW.

This review is for a previous version of the add-on (0.0.0.3). 

Hellow, tnx for review.
* corrected work with file names
* the problem with the file size I do not know how to solve...
helps to reload page

new version https://addons.mozilla.org/ru/firefox/addon/youtube-tools/versions/?page=1#version-0.0.0.5