Update: Stopped working a day after...I don't know what's going on, but it's like youtube knows that I'm using it or something. So now after I downvote it will change, but as soon as I refresh the page it reverts back to where the number was before.... oh well it was interesting.

I actually think it does work. You have to do some password logging in (to check to see if youtube's just honoring your vote while logged in) and out due to youtube's way of displaying the downvotes, but with this app you can see them regardless if you're logged into yt or not which I later found. So when I logged out, closed browser (cookies deleted) and then opened browser to the same vid - and not logged in....I could see the downvote in-fact had changed. I did this with both downvoting and then clearing the downvote by upvoting and it does seem to register my change in the vote.

Stopped working

Been using this extension ever since it same out. Though I know it isn't perfect, it's a solid representation of the actual dislike/like ratio from my experience (videos that are more criticized in the comments tend to have more dislikes). Shame that Youtube removed dislikes, imo it was what set it apart from other social media platforms.

Slows down the entire site during use. It's useful to know when a crappy video is not worth watching, but man, I can't deal with the slowness.