We reported a couple weeks ago that Dark Souls: Prepare to Die Edition had to delay its planned to move to Steamworks.
The patch which is available on Steam will move the game away from GFWL and also allows users to migrate their save games and achievements over to the new Steamworks system. The instructions on how to migrate your data to Steamworks has been made available on the Steam community forums. Those of you that bought the game on disk, through Steam or any other version will be able to do this.
Those of you that purchase the game from now on will automatically get the Steam version of the game without having to patch it or migrate any data which is a lot less hassle.