Ok, I'm a little behind the times when it comes to Mp3 players.  I finally broke down and bought one. There are some things I like about it and some things I don't.  First the complaints:

• It uses the same button for fast forward as it does for “go to the next track.”  This is annoying because if I want to fast forward and accidentally click instead of hold down and click it goes to the next track.  This is an issue because I listen to DotNetRocks durring my commute.  It really sucks when you are an hour into a show and you try to skip over something and all of a sudden you are listening to something else. 
• When you try to go to the next track and you have large mp3's it takes a while.  It took me a while to figure out what was going on.  The player becomes un-responsive as it processes your command.
• The screen is a bit too small. It'd be nice if it was bigger.
• The software that comes with it is lame for managing a music library.
• I wish that it had a bookmark feature, where I could bookmark a file 1/2 way through, listen to something else, and then pick up listening at my bookmark.

Ok, now onto the good stuff:

• The fast forward function (not the button) is nice.  The longer you hold the button down the faster it fast forwards. This makes up a little bit for the lack of a bookmark by making it pretty easy to skip ahead to where I want.
• It is compatible with Windows Media Player 10 which has a pretty nice sync feature.
• It treats the player as a removable drive.  This is very nice.

The only piece that I would really like now is the ability to dynamically create some playlists based on which files are on the player.  What I want to do is scan all the files on the device and create playlists by genre.  After playing around a bit I figured out that the playlists are in m3u format.  This is the same format that winamp uses and the spec. is published.  I found a reference here.

This sounded like a  fun project, so I will be working on an app that will read a directory, scan it for mp3 and wma files, read the tags, and spit out playlists by genre.  If anyone knows of something like this out there, let me know.  Otherwise, I will make another post once I've finished it.