I'm just wondering whether anyone has gotten very far in the Japanese tree or if anyone has finished it? I did some on it and really liked it, but felt I should put it on hold and progress in my easier languages first.
I haven't finished it (I really haven't started it either), but I would advise you to wait until the web version comes out. Right now, since the course is only on the mobile version, there are no Tips & Notes. I think it's pretty useless to try to learn a language without learning its grammar.
I would suggest that anyone who is new to Japanese should view the EN-> JP duolingo app as an introduction to basic vocabulary and to recognizing words that are already written in hiragana, katakana, and a few basic kanji. Without explanations about Japanese sentence structure, particles, and verb tenses, this course as offered on mobile is of limited use to someone who has not been exposed to Japanese grammar. You will also not learn how to write Japanese from the duolingo app, which limits your ability to text or email friends in the target language.
You've made some excellent progress on your European languages - maybe when the web-based Japanese course becomes available, there will be broader support for 日本語 language learners in writing, reading, speaking, and understanding.
頑張って! (Do your best!)
I think it's still going to be worked on but right now I'd focus on learning their alphabet (hirigana & katakana) so it comes easy to you and it'll make learning the rest easier later. Sites like japanese.lentil.com can be a lot of help with this. but I think whatever you feel you can handle.
So far, I've reached level 7 and made it past the second checkpoint. I'm on the skill titled Positions (left, right, up, down, beside, etc.). Japanese is already difficult for the general native English speaker. According to FSI (Foreign Services Institute), Japanese tops the category III (most difficult) list. So, learners should expect to spend about 2,200 hours of actual learning time to get very comfortable with the language. However, Japanese is pretty consistent. So, some people will prefer that to other languages that have irregularities. For me, the most difficult aspect has been cultural context (because there are so many layers of politeness!), how different its structure is from English (subject, object verb, and the particles), and of course the Kanji. I wouldn't let that deter anyone though. Like with all languages, it is a matter of building familiarity with it.
I forgot that I was going to put together some small tutorials. I'll try to remember to get to that later today. :)