How fluent is fluent?
While I am aware that "fluency" is difficult to define, but in your experience, what level of fluency does any given DuoLingo course bring you?
In particular, how complete are the French and Esperanto courses?
Well, with French, I think Duolingo creates fluency to an extent that one is able to write in the language pretty good, as well as translate with accuracy from French to one's native language. I don't think the tree is exactly complete in that the courses primarily teaches vocab with the appropriate rules, but expanded learning like other websites, foreign experience, or textbooks may be needed to be fluent in reality.
Duolingo teaches all of the important tenses. The ones it doesn't teach are either easy enough to figure out (past future) or only used in literature or formal writing (simple past, subjunctive past perfect).
As for grammar and vocabulary, Duolingo provides a foundation strong enough that you should be able to hold a basic conversation. To gain fluency, you should build upon that foundation through further study. I personally use memrise for vocab. This is for French btw. I'm unfamiliar with the Esperanto course.
I completed the Spanish tree and am now studying French while living in France, and I'd echo MasterZsword saying Duolingo gives you pretty decent reading and writing ability. Beyond that--and I know fluent means different things to different people--I don't think Duolingo conveys fluency if fluent is defined as being able to hear and speak the language as well.
That said, most online courses I've tried (memrise, babbel, kwiziq) are almost exactly the same. They focuses on reading and writing, with a small sprinkling of hearing, so that's what you'll learn.
I believe Duolingo only gets us to level A1:
"Can recognise and use familiar words and simple phrases for concrete purposes. Can introduce himself or someone else. Can ask and answer basic questions about home, family, surroundings, etc. Can communicate in a basic way when the other person speaks slowly and clearly, and is ready to repeat or reformulate to help communication."
Look up at the top of your screen where your profile is, roll over your flag and click "add a new course" click on french, and look below the picture. Hoped I helped!
I think a lot of good things have been said here so far, and I just want to add some thoughts. I have been studying French for two years on Duolingo, I have finished my tree and have some a bit of Immersion work. I can hold simple conversations with native speakers, and moderately complex conversations with a patient native speaker. I think that with French in particular there is a difference between reading and writing fluency and spoken fluency. I can read fairly advanced stuff, but speaking is much harder. For me fluency is a matter of goals.
My goals are as follows: (Short-term)
Be able to access new information in French without reverting to English.
Be able to go through all the common tenses with the twenty most common verbs by memory.
Be able to hold a casual conversation with a patient friend.
Be confident enough to open my mouth and speak French the next time I meet someone from France.
Be able to hold a conversation with a native speaker about the legacy and history of Napoleon.
Be able to write passable French Prose.
What fluency rating do these goals get me? No idea, but I chose to shoot for specific goals rather than amorphous definitions. It's what works for me... But you might be different, and that is Ok.
Duolingo is a great tool that will get you down the road to fluency, however deep down that hole you want to go. Be patient with yourself! Don't expect perfection! Think of this... How many vocabulary and grammatical mistakes do you make per day in your native tongue? If you are like me, quite a few; so don't expect perfection in a new language. Work hard, but not so hard that it no longer becomes fun. Read stuff! Find simple phrases you can use every day to cultivate the habit of responding in French. Above all, Never give up!
Merci Beaucoup et Bonne Chance!
Been at 63% for long long time, wonder if I can get any more fluent, but did have a pick-me-up the other day, and a compliment to Duolingo when a French man commented on the clarity of my speaking, where as I had no reference point before, but was happy trying daily to improve.