Matrixofdynamism,
I am also a returning Japanese student and this is the method I find has worked best for me as well. I have spent years starting and stopping my studies due to classes, schedule, life, etc. I am also very frustrated with my lack of progress. So I am sharing with you and others what I found to work best for both myself and my fellow students over the years, some which have become very fluent!
Yes these programs have excellent teachers who will help guide you and answer your questions. Again I cannot speak for J-OS but JOI does have certified teachers and they are able to explain grammar sufficiently.
Also if you are like me at all, you will benefit from regular classes/lessons with a teacher which keeps you on track and moving forward with your studies. I find that even though we can learn as a non-traditional students quite easily, we often get side-tracked on different topics, grammar, etc. In the end our movement in studying is more circular and we make little progress to our goals.
Of course when your an advanced student learning independently of a teacher makes good sense. Especially when you can read Japanese and understand explanations in Japanese as well. A fellow language student I was most impressed with was one who never took a language class in college. However; He told me self study was not his method of success either. It was the fact he put all his money and time into private teachers for one year. He had regular meetings multiple times a week, and in one year his level of fluency was incredible! I saw the same advantage when I studied in Japan, the students who took private tutoring lessons two or more times a week were much more advanced (and even appeared to study less) than those who did not.
think most other students would agree that one-on-one or small group learning is a big advantage to University classes or independent studies alone. I would definitely give it a try. I do recommend JOI or try to find others online.
As a note: I learned from a language instructor that a good rule of thumb with tutoring or private lessons is to take at least 1.5-2 or more classes a week on average to see any real progress. Once per week is only good for practice or maintaining what you have learned, and progress is negligible. It's not the cheapest, but its a heck of a lot cheaper than a university course!
Good luck!
Japanese Online Institute (JOI)
http://www.japonin.com/
or
Japan Online School (J-OS)
http://www.j-os.com/
