Just got my XIII.
First impressions:
1) It's beautiful. It's as good looking as the Sony NW-ZX2.
2) It's better designed than the NW-ZX2.
Now, about the unit itself....
1) It's too slow to be usable. The first time I booted it, I couldn't even select the language. It froze. Then I managed to install it. It took around 10 minutes to install Facebook Lite, Chrome and Spotify.
2) Opening Spotify takes a while, but the bad thing is: selecting anything from the menu takes a while, selecting a song takes a while, selecting a new song takes a while. Everything is DEAD slow. As in "I bought a $30 Android Phone 5 years ago and installed Spotify on it" slow. And no, I'm not exaggerating.
3) Every once in a while, Spotify will quit, and will drop me to the home screen. And the unit already froze on me suddenly, and I had to reboot it. Which took ages.
4) Sound is mediocre. I'd rather listen to the output of my Galaxy S8+. It doesn't have as much output power, and I'm sure it doesn't sound as good as the Fiio with big cans, but with my portable headphones, sound is pretty much the same - but the S8+ is far more stable and quick. The user experience is so far above and beyond the Fiio, I'd rather use the S8+ all the time.
5) NO SYSTEM WIDE EQ?!?!?! My S8+ has it! I need it to use the iSine in-ears - no luck!
The weird thing is - I read so many good things about how awesome this unit was. And I've had nothing but excellent experiences from Fiio products. I have to wonder how many of those reviews were not completely honest. The X5 III, as is, is unusable, IMHO. YMMV, etc., but I'd rather have an LG V10 or V20 than the Fiio.