There's little point in converting your example to DirectCompute. It has no need to share data between pixels, so you are actually much better off doing a global tone-map operator in a Pixel Shader.
A more interesting case would be in trying to do a local tone-map operator where pixels need to share data between them (something you can't do in a pixel shader in a single pass). That's what the classic DirectX SDK sample HDRToneMappingCS11 is doing.
Other interesting DirectCompute shaders can be found in FluidCS11, NBodyGravityCS11, and BC6HBC7EncoderCS. There are also a number of compute shaders in the MiniEngine DirectX demo.
You can look at AdaptiveTessellationCS40 for ideas as well, but it's probably not a good choice for actually implementing tessellation on modern hardware--it was intended as a way to emulate tessellation hardware for Feature Level 10.x cards.
Of course, you can also use DirectCompute for completely non-graphics related tasks. For example, the ComputeShaderSort11 sample which implements a bitonic sort.
Take a look at the BasicCompute11 for a very simple example of using DirectCompute that does a simple sum of two arrays. This sample is really more about how to do all the setup and creating the buffers, so the shader there isn't really all that useful beyond showing how to deal with double-precision data buffers.