Stats work great. Not usually my thing but still interesting to look in to, whether for my fics or someone else's. Main issue right now is that the tag blocking doesn't seem to be at all functional, which is why I added the extension in the first place.
I added as many /Reader -esque tags as I could think of, because it drives me nuts, but in testing, it doesn't seem to function.
The menu shows up as it should, as do the expanded stats, and altered text width, so I know the extension is installed correctly, but those are the only parts that work. Any tag, language, or rating restriction doesn't seem to work at all.
Happy to update my rating once it does what's advertised.

normally i love this extension, as it adds a lot of useful things that i find very helpful. however, it hasn't been working recently and i can't give it more than three stars because of that.

when this extension actually works its a 5/5 star extention but it just. doesn't work

It works well, but don't log in to track your statistics like bookmarked, kudos'ed, etc.
In it's current form, you will receive reading history of other people, not just fics you've read. This gave me a heart attack and caused a whole lot of anxiety, but you can just delete it and then reinstall it. (There's no convenient log out of your AO3 button once you've logged in with the tool).

Would be 5/5 if this bug was resolved, tbh.

all good features but rate-limits the site when used