I just got this little unit today. It's a great size and weight, especially compared to my Pioneer XDP-300R which I find amazing but a bit bulky, and the Hidizs AP80 which I think is a great little unit that's well built but just a little too small for me.
This one is a good size, though still a little on the small size, but I can live with that. Not having a wheel for volume control is a little disappointing but not the end of the world either (all of the last DAPs I've actually purchased (not review units) have had volume knobs/wheels and I love that!
All of that aside, I like the portability and pocketability of this unit a lot. It has enough power for my IEMs but lacks power for my over-ears. My Focal Elex and Elegia had enough power for volume output, but was missing some of the dynamics I am used to when powered by a stronger amp. The XDP-300R, for example, using balanced, works fine for them.
But haven't missed a beat with using them with any of my IEMs so far, so that's really nice. Also LDAC and bluetooth work relatively well with my WH-H900N headphones.
The lack of system RAM is a little frustrating though. Spotify lags and while not the end of the world, when I put it side-by-side with the XDP-300R, which is 3+ years old and runs on Android 5.1, the M6 barely chugs along. I can be in a song playing while the M6 is still loading the app. Everything takes a noticeable amount of time (many seconds) longer to perform when using Spotify and even the stock app compared to the XDP-300R. The 300R has 2GB RAM and uses a full blown mobile processor (albeit quite old now), and not a smartwatch CPU and a minuscule amount of RAM that the M6 has.
The other issue I found with RAM and CPU is the LDAC performance is pretty terrible. It runs alright when using the lower quality LDAC setting (stream preferred), but buffers and distorts and lags when using the higher quality LDAC settings. It's basically unusable with the highest quality LDAC setting.
Anyway, I will have to post a full review in the future. But so far, slow downs aside, the sound and value of this unit is quite nice and could be a recommendation in the future.