i'm a new owner of ak100 for around 2 weeks. so far been loving it. pair with pico slim with jh13/eph100 and for the past few days been using asg1. i've been avoiding high end dap like hifiman, colorfly, dx100,etc for 3 main reasons (in order of importance) :
1. UI - those are terrible terrible UI. If its not idiotic, its slow like hell (in the case of dx100),
2. Size - i dont care if it can sounds like angel singing but if sizes like brick and not pocket friendly, forget it
3. Battery life
AK100 ticked all my requirements above. I've been sticking with mainstream player for all these times with sansa clip being my main player and cowon d2. Love both of players but its just pale in comparison with ak100. That's why I jumped on it.
Speaking about Altmann, i did audience it before I buy ak100. It may hold the title as the best SQ and smallest player of all. But it has the most idiotic UI and support of format. My music collection is all in FLAC and to re-rip it to WAV simply unthinkable for me. Plus price wise almost double. SQ wise not night and day vs ak100. In short I believe ak100 managed to balance between SQ and practicality (UI, size and battery life) as an audiophile DAP.