I'm glad they are not doing a demo
If they release the demo early it would just be frustrating because of the limitations they would need to put on it.(Time/Quests/Area)
If they realeased it after the release date it would make no difference to me for obvious reasons
I say spend the extra time polishing the game even more. Plus there has been some who say that demos don't always help game sales. I think RPGs are games that don't fit well into the demo model due to the importance of the story.