There's supposed to be 16 hours of additional content and footage (4 more hours which are new compared to the original DVD release).
Quote:
Wizard of Oz 70th Anniversary 4 Disc Blu-Ray Amazon Exclusive in LIMITED and NUMBERED one-of-a-kind collectible packaging - Contains 16 Hours of Enhanced Content, Four of Which Are Brand New, Including New Documentaries, Featurettes, Digital Copy on Disc and Rare and highly collectible memorabilia. Premiums include: 52-pg. Production History Book, Behind the Curtain; Exclusive 70th Anniversary Watch with genuine crystals; Reproduction of the original film budget; 1939 Campaign Book. Blu-Ray Exclusive: 6 hour MGM documentary When the Lion Roars. Exclusive to Amazon are a set of 4 collectible poster cards featuring the characters of Wizard of Oz.
Yeah! I'm so excited about that! One more reason for me to watch it. In thirty seven years, I have seen it about seventy four times, and can always use a reason to see it again!