A big thumbs down from me. It wants too much. You have to download and install a video player to view the videos it downloads. The videos I download can be played on Windows Media Player (everyone has that) and Itunes player, realplayer, and others.
That tool bar doesn't give you the ability to download in HD quality from what I read. You don't need a tool bar to achieve this. What you need is to install the Firefox browser and start getting use to that. Then in a few days when you are more comfortable with Firefox click the firefox extension link that I posted above. Download an extension you like and restart Firefox and the extension will be working for you.
When you go to youtube again you will see a download link under the video with options to download the video in the format you want, like MP4 HD, 720P, Mp4HD, 1020p, FLV, etc,,, and audio extracts in MP3 format. It depends on the video and what quality it was uploaded in. Sometimes FLV is all you can get. But search for high quality video of the same thing and download that version. The bottom line is you need the firefox browser and the extensions for what you want to do. Internet Explorer doesn't have these options for extensions.