I've been aggressively studying Mandarin now for about 6 weeks, using a variety of combined sources including Fluenz, private tutoring, mobile apps, and a couple books. My background is that Mandarin will be my 3rd/4th language (after Latin, Spanish, and dabbling in German), and I also work in product design at a bay area tech company. So hopefully I have some relevant and/or helpful perspective.
I've reached a stage where I have some suggestions for the Fluenz Mandarin product. I like Fluenz very much -- it helped me on my beginning journey through Spanish, and it helped kickstart my Mandarin. However, I'm finding myself using Fluenz Mandarin less proportionality compared to other sources, and so here are my suggestions that I feel would keep the product more competitive, especially for a learner using multiple curricula.
1. Be forgiving about which vowel receives the tone marking. According to my tutor (a native Mandarin speaker who grew up PRC), while there is a proper placement for the tone marking, e.g. xiǎo not xiaǒ, and this is emphasized very much in K12 in PRC, for adults it's not paid attention to much, and often the tone markings (when hand-written) are even over and between two vowels, not over a specific one. She says what's important in practice is the tone for the whole word, not which letter it appears over. My suggestion for Fluenz is to copy the behavior I've seen on some websites, where the tone marker vowel position is auto-corrected in real-time as you type.
2. Be forgiving about spacing. If the expected answer is “tài guì le”, I should also be able to input "tàiguìle". If I'm already using an IME, then I have some muscle memory that is slowing me down in Fluenz, having to think about white space unnecessarily.
3. Allow correct recognition of Hanzi characters, in cases where the user is already using an IME and already learning the characters from other sources. For example if the correct response is "méiyǒu", I should also be able to enter "没有".
3a. Allow the option to see Hanzi characters w/Pinyin in the workouts.
4. Teach the third tone rules much sooner. One of my first big struggles starting out, until I realized this from https://www.youtube.com/watch?v=aAqay...
and my tutor, was that I shouldn't be trying to pronounce the full 3rd tone every time I encounter a 3rd tone sound.
5. I'm on the fence about the pronunciations in the recordings. I visited Beijing for 2 weeks recently, and noticed most people pronounce their tones more subtly. I imagine the exaggeration in the videos is to aide with learning, but I think I'd rather learn more a "normal" way of speaking from the beginning.
6. The market I'm sure you're already aware of -- there are complementary learning approaches that involve spaced repetition models, such as Duolingo, or some of the Chinese-made Duolingo clones. Great for maximizing vocabulary retention and learning rate. Maybe a dynamic vocabulary review can be added to the product.
7. Voice recognition for evaluation of tones and consonants would be very helpful. A mobile app I use has this for Mandarin, and it's accuracy (anecdotally) seems about 80%-90%. Good enough to be useful. Where it fails to distinguish are between x and sh, but otherwise useful.
The landscape has changed a lot over the years. I still see value in Fluenz's guided, video & workouts approach, and personally get value from it; however, I think the product needs more functionality to stay effective competitively.
I hope this is helpful. I'm happy to discuss further via email (we've exchanged notes a couple times a few years ago.)