I bought this to replace a much used mp3/mp4 player that had been damaged in use. I use it mainly for listening to downloaded radio shows and also for fm radio directly. I do not listen to music. The device has an operating system that expects you to listen to either music organised into albums or podcasts organised into episodes. My radio shows download as podcasts with the meta data genre set as podcast. This means that in the default state it will play all episodes of one program but not automatically play several episodes of different programmes. It has no file manager function (which I've used for this purpose before) A little research and I have found that changing the genre from podcast allows me to get the functionality I want by saving them into the music folder.
MAXIMUM VOLUME was a problem. If you set the region of the device to Europe then the maximum volume is set to 85db which is fine for listening in a quiet environment but too quiet for any amount of background noise. Setting the region to rest of the world allows a max volume much louder to be chosen.
The necessary research to overcome these problems brings the stars down to 4 on a device which once you have worked out its quirks is generally excellent.