I know the special edition came out in November. Can;t remember about the regular edition. I know it was before Sept. 16 b/c my SIL got it for her b-day.
The 4 disc set had a LOT of extras, I don't know what the 2 disk set has but the 4 disk has extra footage, lots of interviews with the cast, behind the scenes stories and how-did-they-do-that interviews with the special effects people and artists.