Though, if that works, install this deb and you shouldn't have to do it manually anymore: https://garage.maemo.org/builder/fre..._0.3_armel.deb
By default - when pressing the button - it tells MAFW to pause/play the track. If you set the GConf key /apps/headset-control/next-mode to true, a press will result in it skipping to the next track in whatever state the Media Player is currently in (Paused/Stopped/Playing etc.)