Let’s face it, every DAP is going to have ‘issues’. For some it’s as simple as price (too expensive), for others it’s battery, UI, software support, Wi-Fi, BT, input and output options, EM interference... you name it, one or other DAP has it. Up to each of us to decide which combination of pros and cons we can best live with, for the price we can afford, and the sound that most appeals.
I have high hopes from the M15 (Pro). If FiiO continues on the same route of improvent from M7 to M9 to M11, M15 can be a near perfect device. I believe in Fiio.