Comment Signals and slots (Score 4, Informative) 161
You can now use any C++ function as the target of a signal using the new QObject::connect() syntax. This is a huge win because with the new syntax the compiler and linker can check that the connections are valid instead missed connections just causing a run-time error.
The moc preprocessor is still required for QObject derived classes, mostly for the translation framework and also to provide support for the old signal/slot syntax which is still allowed. Qt5 doesn't require a C++11 compliant compiler, which is a good thing since there aren't yet any fully compliant compilers. I'm sure if there is a Qt6 it will require C++11 and use those features.
Some of the really cool C++11 features like move constructors aren't necessary with Qt because it's containers implement reference counted copy-on-write, so when you assign a QMap from another QMap no copy is made, and if the old QMap was an rvalue then there is never a need for the copy to be made when the new QMap is modified. One of the big improvements Qt4 made over Qt3 was to make container assignment atomic so this mechanism worked with threaded code and defensive deep copies weren't necessary anymore.