OK.

Very often the extension shows "Ошибка: достигнут предел использования сервиса. Подождите некоторое время и повторите попытку." instead of translated text

Opens the translated page in a new tab, who would want that?

good plugin. I wish add speaking audio pronounce to it please

No me funciona traducir cuando selecciono un texto

TLDR: The extension will eat up 80% of your ram with only two tabs!
The most awful extension I have ever installed. My PC has been acting stupidly slow for a few weeks and I was like WHAT on earth is going on. I would see firefox taking 6GB of ram with only two tabs. Was about to get more rams till I decided to do so research and noticed some posts about how some extensions can do this. And vollah! This awful extension was the culprit. Removed it and my pc is back to normal. Taught me a lesson though and I'll be careful from now on what extensions I install.

Excellent stuff!