I have used many Sansas, including the excellent E250 and E280, the disappointing View and Fuze+. While the best sound and usability is the Fuze, it is discontinued, but it is SO GOOD a new one on eBay or Amazon can cost anything up to $799.00 (take THAT, iPod). When Sansa discontinued the Fuze, I immediately bought several as backups. I’m on my last one. The only thing that wears down is the headphone plug, where you commonly lose the left track. Sometimes opening the unit and trying to squeeze the too-well-protected jack mounting will cure the problem for a while. At any rate, I just bought my first Clip+ as my last Fuze is starting to get old. First thing I noticed is that it doesn’t support .pla playlists (shame). I have hundreds of audio books on my computer, all with .pla playlists. The interesting problem I’m having is that, when I copy a named audiobook folder into the Audiobooks folder, the Clip+ only shows that folder as holding a book called “Unknown.” The tracks have the right name, and looking at the folder while attached to a PC shows the right name, but in the Clip+, all of my audiobooks are labeled “Unknown” and you have to start each one to see from the track name which it is. Is there any way around this to get the Clip+ to recognize the names of my audiobooks? Should I convert all my .pla files into .m3u files, put them in the Playlists folder, and use that as my launching folder? What a pain that would be. Any suggestions on how to get the Clip+ to recognize the actual folder names in it’s Audiobooks folder?
Anytime the player lists something as “Unknown”, it means it cannot read the ID3 tag of the file(s). Either the tag is in the wrong format, or other discrepancies within the fields of the tag. I’m curious though; I assume these are the same files that displayed correctly on your other players? The Clip+ is not that different, and that information should be displayed the same.
As far as I know, .pla playlists works ok on the Clip+. I only use .m3u playlists myself, so can’t verify that, but I know there are many posts here on the forum on the subject and I don’t recall any complaining that .pla playlists don’t work.
One thing though . . . if you convert your .pla playlists to .m3u, do not put that playlist file in the Playlist folder. That won’t work. Only .pla playlists go into the Playlist folder; .m3u playlists must be in the same [parent] folder as the music files themselves (i.e. Music).
Hope this helps. 
[Edit]: One more thing . . . I don’t believe playlists will work with files in the Audiobook folder. I think they have to be in the Music folder. You might try moving your audiobook folders/files into the Music folder and see if that might not help. 
