i noticed some flacs are prepared badly, so they can sound worst than a good ripped 320kbps mp3, on the other hand, there is nothing better than a good >800kbps FLAC on the Fuze, IMO
Try the little experiment yourself. Rip the same track from one of your own CDs into flac and into 320mp3. Compare them on the Fuze. Report back what your findings are.