Enjoying my x3 so far, only two issues I have with it
1 - File transfer is slow, very very very slow.
2 - For some reason, in category view it orders my songs oddly. I have my multi-disc albums labeled 101 201 etc for disc 1 track 1 disc 2 track 1 and it organizes them in 101 201 102 202 order. Browse files works perfectly though, so I'm using that.
Sound wise compared to my iPod classic it sounds a bit livlier, the soundstage seems much wider and the music seems to have a bit more energy and warmth about it, as well as bass being more punchy. This is with my JH11s, haven't used it much with my Amperiors Momentums or HD600s
I'd say it even sounds better than my classic -> iBasso pb2 setup... But that's from memory having sold the pb2.
For speed I usually just pop the MicroSD out and use an external reader. I got a green one off amazon for like $8 and it has been great, and accepts MicroSD natively.