Full C++11 support is not ready yet with the NDK, and I don't have an ETA, though were working on it (by porting llvms libc++, stlport cannot support it, and the various GCC-version-specific GNU libstdc++ implementations are a PITA to work with anyway).
The platform C++ compiler is currently based on GCC 4.7 so technically supports a few C++11 language features, problems will arise if you try to use certain C++11 STL features though. I cant tell you which, so assume you should not use them, but feel free to experiment.
Exception / RTTI support in the NDK is provided by statically linking the appropriate C++ runtime libraries into application-specific libraries. I don't know if such support is available from the platform system libraries, but LOCAL_RTTI_FLAG in the platform build system seems to indicate so.
If you're building a custom image, you should be able to do what you want as long as you don't modify the NDK-exposed system libraries. This includes /system/lib/libstdc++, which is _not_ a real C++ runtime.
Hope this helps,