This is some feedback regarding offline playlists.
At this very moment I have about 1 400 sons synced to my iPhone 4 and to my laptop. Whenever I close the app or reboot my computer, Spotify decides to unsync a small amount of songs - this is odd and should not happen. This means I can never close the app entirely on my phone because I may have to resync them - which is not something I want to do when I'm on the go.
Since this idea was created there has been many updates.
If you're still experiencing this bug, please feel free to create a new topic in the help forum about it. Thanks! ;)