As far as the C++11 library support, Clang's libc++ has always been far ahead of GCC's stdlibc++, and it still is: there's still no unicode codecvts in GCC, and barely any regex, and many other omissions.
I use (well, experiment with) it on linux at home. I build libc++ from SVN (and it has a few rough edges where it relies on Apple's BSD'isms, e.g. when figuring out POSIX equivalence classes).