It looks look DirectX 11 is shaping up to be a real upgrade from DirectX 9 and 10. Here's a few features that Microsoft focused on during the announcement:
Microsoft will add new "compute shader technology" which will be utilize video cards to run parallel with your processor.
New multi-threaded resources allow developers to take advantage of multi-core processors much easier.
Support for tessellation, which blurs the line between super high quality pre-rendered scenes and scenes rendered in real-time, allowing game developers to refine models to be smoother and more attractive when seen up close.
Some new DirectX 11 features will be compatible with DirectX 10 hardware, along with extra features for DirectX 11 video cards. Microsoft plans to release it before Windows 7 is out, so we should expect it sometime next year. These are just a few of the details of DirectX 11, expect more as Microsoft announces it.