It was a while I wanted to get a mp3 player ...
and then I decided to buy an Apple iPod shuffle 512MB
Here are my comments :
Pros :
- the sound is really excellent, this is still hard to believe for me
- no external battery is required, just load it when connected to an USB port
- no need to reload often
- shuffle is an option only 
( I was mislead by the description on the web site ... it is possible to choose between shuffle mode
and normal mode )
Cons :
- all mp3 players I know play a small blank between each tracks, which is pretty annoying when listening a Pink Floyd album ... iPod is unfortunatly not an exception 
- IMHO iTunes is not that user friendly ... i could not figure out how to change the order of the songs within one album ( e.g. directory )
- when pressing the 'next track' button several times, results are pretty random ... looks like some actions are discarded
Conclusion
iPod shuffle is really an excellent product which does what is supposed to do : play music with a great sound quality !
I found some minor things that could be improved ... nethertheless I am very happy with my iPod shuffle and I will recommend it to
anyone looking for a simple mp3 player