My M5 arrived from Amazon US this afternoon. I've been playing with it at work this afternoon. So far kind of disappointing. I will not be able to update the firmware of the player until I get home so maybe it will improve but the overall lag with the M5 is pretty bad. I'm not just talking scrolling through music, it is with all the settings too. Way too long between touching something and waiting for the screen to change or the setting to be changed. I am using the M5 with a 128gb sandisk memory card that has about 12,000 mp3's encoded at a variable 256 bit rate. It's basically my whole music collection. The sound is a little brighter than what I am used to from Fiio actually and it's pretty good. As a BT receiver it worked fine with my Android Oneplus 6t phone. It connected using LDAC and sounded good. I will play with it more when I get home tonight after I update to the new firmware. Just wanted to give a brief first impression.
I'm honestly not that surprised. It's a $100-ish unit, and even expensive $500 Android-based DAP's tend to be slow and clunky more often than not. Personally I want it most for the bluetooth receiver/transmitter stuff. Anything else I'd consider a bonus.