I never purchased any additional content for either Morrowind or Oblivion. Skyrim will have to offer something very special, both the core game and additional content, if that trend is to change.
We already have a very active thread ongoing about this very subject on the first page of this forum. http://www.gamesas.com/index.php?/topic/1174292-so-whos-disappointed-with-how-bethesda-will-handle-dlc/ it is, no need for multiple polls about the exact same thing.