The idea is for 5 stars for sure. On chrome it seems to work pretty well. However, on Firefox it is kinda buggy.

Sometimes changes are not saved in spite of the fact the notification pop up explicitly says that changes have been changed. Sometimes you need to refresh the page to see the subscription list. Sometimes it works okay. Tried to disable other plugins, but didn't solve any issue.

Will keep using it for a while though.

-- edit --

After using it for a couple of days, it certainly deserves 4 stars, so I increased my rating from 3 to 4 stars.

Just for reference, the problems I describe above are in my Linux systems and in more than 2 (fully updated) computers. The problems mostly occur when i massively change the categories on the channel list. Apart from that, everything else runs smoothly.