update 2-13-22:
less and less universally working. Does not work on many pages and does not give translation for cebuano or filipino. Better than the others I have tried though.Need to add translation of entire web page that works. Google does not work often.
started out good about 4 mos ago, now getting flaky. Icon appears without input. some pages cannot send to translation or does not work when translate page is activated. Still pretty good though but not as convenient as I first thought. Still having to use an outside translator, particularily for webpage translations.

It resets nearly every day the Settings & Languages (sometimes even at the moment when I use it), thats extremly anoying

Text to speech is limited by 200 characters. It is not really useful for reading full articles

- When using Etherpad it pastes unwanted text in the text field when you type. So I have to disable this add-on when using etherpad.

- Pop-up mode doesn't work with Twitter.

Llevo años con la extensión, pero, ahora me bloquea los botones de Gmail y otros botones de varias páginas. Desafortunadamente, me tocó desinstalarlo.

В 15.54 всё равно не работают чаты на tradingview.com. Сообщения в чатах не отправляются, плагин мешает.

Il manque plus qu'une petite option dans les paramètres pour redimensionner la fenêtre quand elle s'ouvre pour la traduction et là elle sera plus que parfaite.

This extension has an ugly "speech bubble" icon in firefox — please go back to the pretty blue "google translate" icon picture.

EDIT (reply to dev response): then why is the blue icon still all over the extension's firefox addon website? I was surprised when I downloaded the extension and was surprisingly confronted with another icon. If it's good enough to lure users with it then it should be good enough to be available in the users' interface.

Good but, it not include spelling for each word.
And it not work in private mode.
Please fix these problem, thank you so much.

The core functions are very well built and work as intended. Just the UI has a lot to be desired. The settings UI is even worse, it is very confusing and doesn't lay out what each option does nor do they all work as intended.

For future, I would like to have certain language pairs always coupled with a certain translation provider. Like for example Chinese to English is miles better on Bing but the UI first always makes me see the bad translation of Google.