The main decision to do a user oriented translation tool, earns 5 stars from my side.
I appreciate especially that the Firefox team included Ukrainian and Persian in this first edition. CUDOs !!!

I'm impressed by how well it works for an offline translator. Amazing.

Depuis le temps que j'attendais ça ! Je vais enfin pouvoir désinstaller Chrome définitivement !! C'est encore perfectible (notamment au sujet du temps de la traduction, ou alors je n'ai pas eu de chances), mais je laisse 5 étoiles car j'ai entière confiance en l'équipe de Mozilla !!

Very useful

Sehr erfreut und dankbar! Helmut

I think this is going to be my main translator from now on, even if it certainly needs improvement (I might use another one in specific cases).

Right now, the translation bar is indeed not the most elegant, but the option to hide it is fine.
There's a little icon next to the address bar (which I didn't notice at first) to make it reappear at will.

Oh, and this text was translated seamlessly by Firefox :)

flawless

Estou amando a extensão, só precisam ajustar a mesma em sites como Stack overflow.

I liked so much the add-on, but the extension has a bug in sites like Stack overflow, specially in code examples with syntax highlight.