The Apple-sponsored open-source Clang compiler has been maturing with LLVM in a steadfast manner. It was just two years ago that Clang was deemed production ready and only one year ago the C++ support was deemed feature complete. In early 2010 it reached a point of being self-hosting, in the second half of 2010 it was possible to build the Linux kernel with Clang, earlier this year Clang could build Qt. It was also two years ago that FreeBSD began planning for Clang to replace GCC in FreeBSD base. Clang is also being widely used for its OpenCL front-end.
One of the latest hefty open-source projects that's been striving towards building under LLVM/Clang is LibreOffice. During the recent LibreOffice conference, it became possible to build the LibreOffice code-base on Mac OS X with Clang. Caveats though include external patches needing to be applied against LibreOffice for the time being, and the generated executable evidently doesn't work at the moment. However, no patches against Clang or LLVM need to be applied.
Details on the LibreOffice Clang effort can be found on this Wiki page.
The release of LLVM/Clang 3.0 is imminent, so new benchmarks will be coming soon -- plus looking at the AMD Bulldozer architecture performance under the various open-source Linux compilers.