Nemix said:Peripheral Compatibilty.
-Classic Controller can't be used with Gamecube games, Wii system memory can't used to save Gamecube games, SD Card can't be used to save games, Wii remote can't be used to reset or access system menu in Gamecube mode, normal USB keyboards and ethernet adapters can'y be used...
A solution for one of those issues (which I agree is pretty farking dumb on Nintendos part)
http://uncledim.narod.ru/wcc2gcen.html