There is absolutely nothing to complain about sound-wise. It's as simple as that. The 600 uses an innovative and effective control panel. Instead of standard buttons, the controls are arranged in a circular layout and rubber coated. It's sort of like a smoothed out D-button on a game controller.
All controls work very well.
It shows track number, title, artist, album, time, encoding rate, and volume. Unfortunately it does not show the time. You must go to the preferences tab for that. There is no FM tuner, no voice recording, and no PDA-style goodies. So while the 600 is one of the best sounding players I have used, and certainly the loudest, it is just too plain.