as a zealous fan of portable C++ :) I recommended to my boss to try to implement one project with C++11 and Boost(Instead of relying on #if and OS specific stuff), and Im confident we can do it with C++11 + Boost.
Now (as a fan of generalizing:) ) Im wondering what are the things that can't be done portably with c++11 + boost.
Afaik std::atomic removes need for Interlocked*, boost has ASIO for sockets, std and boos have threads and mutexes, boost has filesystem...
EDIT: ignore reality of partial support of C++11, lets assume total C++11 compiler support.