Most needed functions are paywalled. Some are not (hence the second star). Seems too bloated If you just want to use the free options -- frequently you stumble upon something that only works when you pay money.
Would use a clone of this with just the free options -- it probably would deserve at least 4 stars.

The `watched` status is not handled properly, and in two ways.

On the subscriptions page, it seems like the Hide Watched checkbox needs to be re-applied for the filter to work, the Play All button here does not work.

In a Channel Group page, the Watched tab doesn't remove watched videos from the list.

Header in subscription list (that permits to turn on and off each category) works in Chrome, not in Firefox...

How do I restore the grid view to the subscriptions page? Not even disabling or removing the add-on did it. :(
Edit: the grid/list options now suddenly appeared after I refreshed the page once more. :/

It doesn't work on firefox. Console spams "Uncaught (in promise) Error: Could not establish connection. Receiving end does not exist.
updatePopupStats moz-extension://76eca0c8-522f-405e-81d8-feae8afbc3c4/lib/ui-service.js:231
ui-service.js:231:25"

Грузит процессор на 30 %, после отключения все норм.

used to work but now it doesn't even show up on my you tube i installed a older version specifically 8.014 that version seems to work but none of the newer ones work
it has three Warnings listed

Reading manifest: Warning processing options_page: An unexpected property was found in the WebExtension manifest.
Warning details

Reading manifest: Warning processing oauth2: An unexpected property was found in the WebExtension manifest.
Warning details

Reading manifest: Warning processing key: An unexpected property was found in the WebExtension manifest.

the console also shows this error
Uncaught (in promise) Error: Could not establish connection. Receiving end does not exist.

extension no longer works

После обновления оно перестало работать.

Love the add in but all of a sudden I can't add new sites to subscription groups in Firefox. I am able to add the groups in Chrome though. Any ideas?

Update 7/8/18:
On 6/13 I sent the developer a couple of screenshots because he requested them in a private email he sent me on 6/11. I am assuming that he received the email. I have not heard anything further from the developer regarding the issue I presented. I am still hopeful that there is a resolution to my problem. I have removed another star from my review, I will be glad to give 5 stars once the issue I am experiencing is resolved.

Update 7/25/18:
Since I still haven't received a response from the developer I uninstalled the add=on and then reinstalled it. This did not correct the original issue. I noticed that even though I uninstalled the add-on the subscription groups I created were still present after I reinstalled it. I wonder if there may be a limitation to how many subscription groups or subscriptions you can have in Firefox. As I originally stated I do not have this issue in Chrome.

Used to work great, now I get errors from Firefox that this script in particular is slowing down the page. I have to temporarily disable it to watch a video or even get a channel's homepage to YouTube to load. It even does this if I have the side panel closed. I have 564 subscriptions and I am using a 64-bit version of Firefox on Windows 10 Professional. Not sure what's going on beyond that. Very sad, though.