I really dig this extension/add-on. It is quite unique and not at all difficult to figure out, well, mostly. Great addition to my browsing experience for certain.

Thanks Taylor and crew! (if there is a crew)

Giving 5 stars for the concept alone as it is amazing and actually lets you just unconsciously soak foreign language just browsing the web. And it works. However, performance does leave something to be desired but i expect it to change soon.

Love the extension, love the idea behind it and I think it will keep being polished and getting better over time. The thing is, I am currently learning Japanese, in Microsoft Edge I had the change to switch to Kanji but I do not seem to find that option on Firefox...

Amazing concept but inadequate implementation. Instantly slows down certain pages (for example the interface of DiskStation Manager) to the point of becoming unusable. Firefox also notices this and asks me if I want to stop this extension from running. This, however, doesn't solve the issue. The only solution is to manually disable Toucan before visiting the problematic page. Can't add the page to the blocked sites because it doesn't allow adding IP addresses instead of domains.

Good idea, but
1) I could not feel significant progress so far (will report back in a few months)
2) as regularly mentioned, performance issue, especially apparent on sites like goodreads

Great idea and implementation is fine, But it doesn't work for me sadly. Even after changing the language in account settings page (and in the initial setup page) to German, it still changes back to Spanish in my extension. When I click Change in the extension, the page it takes me to shows the correct language (German). I tried restarting and reinstalling but sadly it didn't work for me. I would prefer if there was a way to de it directly from the extension instead of redirecting me to a page where the changes I make don't get reflected back. I'll definitely try it again in some time because I love the idea, the implementation could do with a little polish.

Good

Toucan is an excellent concept. Unfortunately, the implementation suffers from severe performance issues, typically on websites with a large amount of content and particularly so when large amounts of content are updated by a script (you can see this very well on api.rubyonrails.org when searching).

This addon works as it says. One caveat (at the time of writing) is that sometimes it slows down the browser to a standstill. I've been told, that they're working on it though, so one can hope. You can disable it on specific sites, or entirely, if you do not want to deal with it for a while.

Toucan is a great tool for learning new languages in truly immersive mode.

I was very excited to use toucan but since I started using this app 19 days ago it's been using so much memory that sites can't load. I turned it off for a while in hopes it would get fixed but despite being an excellent idea for an app, it doesn't really matter if the sites it translates don't load.

Fantastic product that doesn't require you to allocate specific time to learn a language - but rather it's seamlessly embedded in your day to day. Thrilled it is integrated into Firefox too!

Awesome Addon!
But please consider: It's still in it's early phase. There will be more in the near future i believe.
I use it to learn italy right now and that works fine on english websites.

I use Toucan to learn Japanese and so far, my experience has been great! Of course, like any other language learning app, there are limits to how much of the language you can learn through it, but as far as learning vocabulary (and in the case of Japanese, the alphabets) goes, I think this is a fantastic concept!
Of course, since Toucan is an ever-developing add-on, there are things I would like to see that would make it an even better experience, such as including some kanji along with the hiragana and katakana in the case of Japanese, or translating some phrases to immerse the user even more in aspects of the language such as syntax (but I realize that is probably much harder to implement).
The dev team is really communicative and it seems to me that they really care about providing the best possible user experience, which is another huge plus. I'll definitely let them know about what I feel is missing in the current version.
Full disclosure, the Toucan team generously supplied me with a month of premium membership to fully try the add-on out, but I believe that everything I said also applies to the free version.