Unity 4 introduces ability to use DirectX 11 graphics API, with all the goodies that you expect from it: compute shaders, tessellation shaders, shader model 5.0 and so on.
To enable DirectX 11 for your game builds and the editor, set “Use DX11” option in Player Settings. Unity editor needs to be restarted for this to take effect.
Note that DX11 requires Windows Vista or later and at least a DX10-level GPU (preferably DX11-level). Unity editor window title has “<DX11>” at the end when it is actually running in DX11 mode.
Compute shaders allow using GPU as a massively parallel processor. See Compute Shaders page for mode details.
Surface shaders have support for simple tessellation & displacement, see Surface Shader Tessellation page.
When manually writing shader programs, you can use full set of DX11 shader model 5.0 features, including geometry, hull & domain shaders.
Currently some parts of surface shader compilation pipeline do not understand DX11-specific HLSL syntax, so if you’re HLSL features like StructuredBuffers, RWTextures and other non-DX9 syntax, you have to wrap it into a DX11-only preprocessor macro. See Platform Specific Differences page for details.
The following screenshots show examples of what becomes possible with DirectX 11.