I started with Alemania in Feb. The books are fantastic at the lower levels. You can practically teach yourself the material with it, and they are the institutions own book series. I had 2 teachers while I was there. The first teacher was ok in the beginning, but I did not realize how bad he really was. He spoke to fast for people trying to learn a new language, and even today I still have trouble understanding him. He is Swiss (german), but his accent makes it hard to understand. In my second month with him, I realized what the problem was, and myself and some other students spoke with him individually to see if he could at least slow down some. He did not change, so I did. I requested a different teacher and he was fantastic! Great book, great teacher, who could ask for more? Well, the new teacher moved on to a different school outside my traveling distance, and I did not want to go back to the bad teacher, so I (and some others) moved to FT. All in all, I did learn a lot from the learning material, but after 3 months I was barely composing sentences to speak with and could not understand what I was hearing. Assuming you have a good teacher, I highly recommend Alemania as a beginner school for learning german, because of the language material covered and the quality of the material. I have kept in touch with friends I made who stayed, and the books change in the more advanced classes to a series from Heuber. The advanced books also seem excellent.
As for Flying Teachers.
It is cheaper! But the books for the beginning courses are horrible. The books do not have a good balance of information, so it relies a lot on the teacher to provide the supplemental information to really learn the grammar (IE-It will introduce a new grammar concept, but only have one example that doesn't explain it well). The reason FT is cheaper, is because it is a launching point for teachers, so you are in no way guaranteed to have the same teacher from one class to the next. On the plus side, my first teacher was excellent. I have heard the same from other friends that their are as well, but I have since had one teacher who was very bad, and one who was just very new. The bad teacher you could tell was there to make some side money and figured it would be easy, so she was extremely unprepared for having to fill in the blanks with a bad book. On the plus side, the book changes in the advanced courses. The new books are very good, and have a lot of great information in them. With a "new" teacher who does nothing more than teach from the book and help clarify things, anyone can do good with them. As a bonus, all the books are published by other companies, so you can pick them up cheaper at any book store.
So in summary.
If you have some social outlets where you can get some converational practice, and you don't mind having different teachers month to month, and doing extra work to fill in the gaps, FT is a good deal. It's 2/3 the price of Alemania and is the cheapest around. The higher level courses are better than the lower level courses (The new book gets introduced after 6 months)
If you can afford to pay a little more, and want a better method to learn by, I highly recommend Alemania. The books do all the work, and the teacher provides all the bonus. If you are like me and don't have a social outlet to practice speaking, Alemania has the right tools to at least get the ground rules stuck in your head. The higher levels utilize a book that I think looks fantastic as well, tho I have not taken those level courses there.
(As of this writing, the courses at Alemania with materials ran 690 CHF against 440 CHF at FT)
Again, as you can tell from my review, the quality of your education really comes down to what teacher you get. But the learning materials do make a big difference as well.
Good luck german language learners!