I have a premium account, and I've made a number of playlists available offline. I have a number of these playlists set to sync with my iPod touch, which I do over wi-fi. What often happens, though, is that only a handful of the tracks on each playlist actually sync to my iPod, while the rest don't. It seems to me that the ones I've recently added to the playlists are the ones that get left out. I don't know what's going on. I've got plenty of space on my iPod, so it's not that.