Well written and fair assessment.  Only caveat is that trying to describe the audio characteristics of a DAP seems to me to be very dependent upon the headphones used.  Some published measurements show the frequency response to be basically ruler flat.  Some of the nuances you report I don't find.  No mid veiling or treble loss of details here.
 
I am one who hears the pitch error but only with a very few select songs.  Given that, I am extremely pleased with this DAP and have hopes for future refinement/enhancement given xDuoo's history with their X2 DAP as well as the prospects for Rockboxing this puppy

Thanks Bob for your kind words - I've made a few minor revisions (this review will probably be a little bit of a work in progress).  I find the treble and mid-range issues to be very subtle (and at this price point I'm being unreasonably nit-picky...).  As I now say in my review, it's more a case that just sometimes I'm aware that my attention has drifted a little and it seems to be because of the very slight loss of detail in that area.  Bear in mind:
  a) that this is relative - normally there is such a wealth of coherent information, that even a slight veiling is still "good".  I've listened to plenty of sources that at their very best sound worse that the X3 at its worst... If that makse sense...?
  b) this is subjective.  One of the things Hed-Fi has taught me is that we all of us hear in remarkably different ways.  It would take a bolder man or woman than me to categorically say, "This is right, and that is wrong."

An honest review and even if mine cost a lot more with its case I think it was still extremely good value for the money. I agree that we all hear different things in tracks that either appeal to us or put us off the track. I imagine it is why so many genres of music exist. I cannot seem to put the player down - the tracks I listen to just sound so much fresher and detailed to my ears.
I cannot really say I can hear the pitch difference, I know it is there so believe I should be able to but this is probably all in my imagination. 

Great review. Thank you. May I know how it performs as a dac? I am interested in using it not only DAP but external DAC for my computer. Will it work? If so, how good it is as a dac? Thank you.

Hi Decommo.  Thanks.  As you'll have no doubt learned from the thread about this player, it doesn't support a DAC function.  I believe that would require physical changes in the hardware.

Thanks for the excellent review. I currently have an iPod which I play in the car. However I need a unit with greater storage capacity. My questions are (a) does xDuoo X3 have bluetooth connectivity and (b) if not, do you know if it would be possible to play it through my car sound system. Any advice, suggestions etc most welcome. Thanks, Nigel

Hi, thanks for the positive feedback. No, the X3 doesn't have Bluetooth. It does have a line out output, which would work if (and only if) your car sound system has a line in input facility - some do and some don't. You would need to check. There's sometimes an input socket on the head unit.