The headphones supplied by Creative Labs are not bad but they aren't all that great either. The musical rendering is metallic and lacks definition, so it's not great. Of course, most users will have their own headsets. And that's what I would strongly advise you to do, whichever personal stereo you use, because the headsets supplied are rarely of high quality. Furthermore, a headset lasts a long time and performs lots of services apart from being used to listen to a digital stereo.
A good quality Sennheiser button headset costs around 30 euros which is by no means a ruinous price. If you use such a headset, the musical quality produced by the MuVo NX will be better than that of the previous version. Reproduction is faithful and natural, and there is no loss in a particular register. The sound image is also neutral, which makes it possible to fine tune it using the equalizer, depending on the type of headset you are using and music you are listening to. What's more, if you are listening to an MP3 file that is not heavily compressed, you will find that the variations in intensity in music, such as in an aria from an opera, are preserved. There is no interference or crackling to spoil your pleasure, the circuits and the analog converter are well made.