(note based on v1.1.4)
The first translation in a language is a bit long due to the download of the model, that would be great to speed-up this process.
Also waiting for the ability to translate a text selection.

That's not too much language which I can choose :(

It only allows translations in one direction that is to english and i can't translate from english to spanish that's i need.
Might be it's not working

i wish this add-on will support more language than this and have button translate like simple translate add-on

In der Praxis erscheint am oberen Bildschirmrand lediglich eine Fehlerleiste "fxtranslation-notification". Schade, die Idee ist eigentlich gut, aber das Add-on sollte vor Release getestet werden.

Please add support to android

Disappointed. What bar is this that opens in all the pages? Do it subtly. By right mouse click.

The translation works well, but I'd like the possibility to translate only the highlighted text

不支持翻译为世界上14亿人口使用的语言，给最低星。但是因为扩展自身UI支持了这门语言，多给一星。

Todavía le falta exactitud en las traducciones, al momento de reconocer los signos como las comillas. La traducción no los reconoce.

The translation is terrible of all the languages, only works Bulgarian!

Been waiting for proper in-page translation on Firefox for a long time. It's not perfect, but it's really solid.

Interesting!

disapears under page-actions buttons on urlbar, is it possible to have it as a regular extension button on the right side please?

Extension pas vraiment fini, je regrette qu'il n'y ai pas le Français, mais je pense que bientôt ça sera parfait.
Bon courage aux dévelopeurs

Inglês para português parece ser até melhor que as traduções online. Muito bom mesmo.