At XDC2013, Stellard shared that Clover currently works with AMD Radeon HD 5000 through HD 7000 series hardware and supports most run-time API features, 32-bit data types, and constant/global/local memory spaces. Among the applications that work with the open-source OpenCL stack right now include Bitcoin mining with BfgMiner, Piglit regression tests, about 50% of the OpenCV test suite, many GEGL/GIMP filters, and possibly other CL workloads. That's where the open-source OpenCL stack is today, which is still a ways off from the proprietary Catalyst driver.
Among the current focus by Stellard for improving the support is handling of OpenCV (the Open Source Computer Vision Library), supporting the OpenCL ICD for the next Mesa release, dealing with DRM Render Nodes support in Linux 3.12+, image support, and supporting more hardware like AMD Sea Islands, Nouveau, and LLVMpipe for OpenCL CPU support. Tom is also hoping for the LLVM to TGSI back-end, new compute flags for Gallium3D, and more Piglit regression tests for verifying their OpenCL support.
More details on the current Mesa/Gallium3D OpenCL support state can be found by the PDF slides embedded video below from XDC2013 in Portland.