I would very much like it if Fluenz would dedicate an entire lesson to German colloquialisms. Perhaps, German six. While these are not sayings that directly affect your ability to speak the language, they are inherent to the culture, much as they are here in the USA. Such as, "jumping on the bandwagon," or "get your goat," or "to steal your thunder," or to "upstage."
These are very commonly used phrases that many Americans have no idea from where they originated, BUT, they know know how to use them very effectively and do so very frequently.
The same is true with German. Short of actually living in the culture for an extended period, no one can understand the meaning of such phrases. Therefore, although you may be able to speak German fluently, you do not understand the colloquialisms or common phrases so inherent to the language and culture. This puts you at a disadvantage and one that no language program has addressed.
I would like to see Fluenz address this with an entire course dedicated to this subject. In my opinion, this is just as vital as learning to speak correctly and appropriately. This is an inherent part of language and culture. It should not be ignored at the expense of formality.