ExtremeTech discusses some of the things they heard about DirectX 11 at NVISION last week, you can read it over here. The article talks about the new stages in the DirectX 11 pipeline, hardware tessellation, compute shader, multithreading and dynamic shader linkage and improved texture compression.
There are three new stages in the standard graphics pipeline: the Hull Shader, Tessellator, and Domain Shader. In addition, changes have been made to the pixel shader to enable compute shaders (for general purpose applications). We'll touch on those shortly.
In addition to the new pipeline stages, DirectX is being tweaked to fully support multithreading. So DirectX 11 DLLs will spawn threads as appropriate on multicore and SMT-enabled CPUs.
Another key new feature are several new texture compression formats, which enable better image quality, and will support high dynamic range. Again, we'll touch on this in more detail a bit later.
Microsoft also confirmed that some new elements of DirectX 11 will also run on DirectX 10 hardware.