At first, I thought this extension was great; it was doing exactly what I've been wanting from YouTube all this time: hide videos that I've already watched and that I'm done for, and also make space for other recommendations that I'd be interested in.

Unfortunately, the extension doesn't discriminate whether videos have been completely or partially watched. This means that it will also hide all partially watched videos from all possible pages on YouTube. This is a problem if you're in the middle of watching a long video and weren't able to finish it. Usually, these would (re)appear in your recommendations to remind you about finishing them; however, with the extension installed, all those videos will be hidden too and the only way you could keep track of them would be by bookmarking them and remembering they're there.

In addition, this extension creates all sorts of glitches all across YouTube, such as preventing playlists and the recommended videos rail to appear on video pages.