Full DVD video playback natively in Director. It will maintain aspect ratio, audio sample info, original size, and full event notification as DVD navigation occurs. The movie (.dcr) can be played in a browser and will still interact with local DVD content. This means you can display info on the web and use content from the DVD — extremely rich content with no download.
Performance of Flash elements in Director. You can now group flash sprites so they all play under one common player. This fixes the huge performance issue for a lot of flash sprites on the stage at once.
Javascript syntax in addition to Lingo. You can mix javascript/lingo within an application, but not within a single script. This should lower the barrier for Flash/web developers to move to Director.