I purchased this little player few days ago just out my curiosity. Cowon offer generally good players and this one is not according to me exception. It has only inbuilt memory 16GB or 32GB which can not be extend with any memory card, it has only very basic, but good and quickly working UI. Load music in to memory takes time, but after that UI react quickly. Start is in 2sec. There is no classic Cowon tools for music adjustment such as BBE, etc, but U7 offer kind of user equalization. In my opinion is better leave setup on FLAT.
Sound is nearly neutral with slight tilt to middle band. It is tonally very close to Shanling M0. U7 send to earphone good amount of tight and precise bass, clear midis and enough sparkle on top end. There is plenty of details and with right earphones you can enjoy each single instrument, each single tone. Soundstage is wide, but I do not feel much deepness.
U7 remember last position, so it can be used for audio books as well. Specification show live time up to 15 hours, according to my experiences is that a bit on ambitious side, you will get more likely 8 to 10 hours as max with mix of format quality. U7 will not recognize DSD, or higher quality of FLACs formats.
It has no any BT, WiFI or other stream capabilities. It is nice, stylish, small and very good sounding EDC player for sport, traveling or simply on the go offline listening. In the past I have tried similar players as iPod NANO, Lotoo PAW Pico, Walnut V2s ( bit bigger ) or Shanling M0. From technical perspective is M0 winner, but if you will not care about BT, DAC capability, etc and most of your music library is in MP3 or lower FLACs, U7 will give you plenty of joy of your music.