My player has basically 2 build quality flaws: 1- there seems to be something loose inside of it; I can only notice it if I shake it; and 2- the "up" arrow doesn't always work correctly; it is tricky to press it correctly. But the sound quality is phenomenal. I agree with all the good reviews.
 
I can't seem to be able to add to the comments section. Answering AmberOzL: just yesterday I used it from having a full battery until it depleted and it lasted about 4 hours; but my files were a mix of FLAC, WAV and MP3.