In my experience it vastly depends on the age of the software product/project. Most new projects that I am aware of do use modern C++ (RAII, STL, Boost). However, there are many C++ projects that are more than 10 years old, and you don't see modern C++ there.
Also, keep in mind that some of the most popular STL implementations were pretty much broken until maybe 5 years ago (MSVC < 7.0 and GNU < 3.00)
