Last year I wrote that larger parts of Qt 5.0 would be written in C++11 (formerly known as C++0x; more of KDE5 Frameworks are also expected to take advantage of this latest C++ ISO update). With Qt 4.8 they began to take some use of C++11, but not a whole lot. Qt 5.0 Alpha took advantage of more C++11 and the usage of this latest language specification is only increasing.
In a new blog posting are details about the C++11 usage within Qt 5.0. Among the C++11 features being taken advantage of for Qt 5.0 include lambda expressions for slots, UTF-16 unicode literals, the constexpr keyword, static_assert, virtual function overriding, final attribute, and deleted functions/members.
GCC has been improving with its C++11 language support (especially with GCC 4.7) while LLVM/Clang also does better C11 and C++11 support. KDevelop also has basic C++11 support when it comes to an open-source IDE.