I have an Opteron XP64 machine with an NVIDIA graphics card and an ATI graphics card. I started with the NVIDIA graphics driver with working OpenCL support installed.
I installed the AMD 2.01 developer package and samples. The OpenCL.dll library in \windows\system32 (that was placed by NVIDIA) was not replaced. When I ran the CLInfo sample only the NVIDIA device was listed.
I uninstalled the AMD 2.01 developer package. The uninstaller removed the OpenCL.dll placed there by NVIDIA. At this point OpenCL programs on the system (like CLInfo) couldn't run because there was no longer a OpenCL.dll on the system.
I installed the AMD 2.01 developer package again. OpenCL.dll (the AMD version) was placed in \windows\system32. When I ran CLInfo only the AMD CPU and GPU devices were listed (no NVIDIA).
I didn't think the situation could get worse than it was in 2.0 but it did. Please sort this out with Khronos and NVIDIA.