At http://blogs.msdn.com/vcblog/archive/2010/04/06/c-0x-core-language-features-in-vc10-the-table.aspx there is a table showing C++0x features that are implemented in 2010 RC
I think I found the answer. I found "enum class" in the VS 2010 documentation under the keywords documentation. It's managed only--unsupported in real C++ builds. So it seems that they mean this C++0x feature is "partially done" in that it isn't done at all.