Right now I don't believe that you can do that. AMG will set me straight if I'm wrong. AFAIK, no program can strip playlists off of the iPod and create .m3u files. It's because they are stored in the iPod's database and not as .m3u files.
Yeah that sucks bad..
XPlay should fix that on their next version. This is what it should be like: Drag a .m3u playlist into any of the directories on there, and it should copy all the songs accoridingly if they're not there, and generate a playlist identical to the one desired. It sounds pretty simple and straight forward to program. I think.