I have a Nano and I had a similar problem. I manually select the music I want on the iPod (rather than use the auto download feature) and when I don't want certain tracks to be on there, I just click on iPod in the iTunes menu and select the tracks I no longer want and click the delete button my keyboard. The funny thing though, is that although the tracks are deleted, the playlist remains (despite it being empty). The only way I can get rid of the playlist is to restore the factory settings and it clears everything although I have to download all the tracks I do want, again. I don't know if the mini works the same but it might help.