Well, from what you're expecting what would be really needed is an improved version of ld, which is part of binutils. Now, about the file size for C++ programs, the only way to reduce it would be creating DLLs of libstdc++ or trying to use a recent version of msvc*.dll, but both approaches are problematic, and GDB is another piece of software too.
It seems GCC 4.x will take some time to be supported by MinGW. The release of 4.2.0 is getting close and I have my doubts MinGW release it... but I think I'll do :wink: