What I like the most is the abstraction-away from plaintext source files. Imagine a C and C++ IDE that hid the (often ugly) source files from you put only exposed individual function definitions - it could automatically keep header files in-sync, for example, and automatically place each free-function or class member in the right file without manual refactoring.
(I still think it's outrageous that C is still a single-pass language - we shouldn't need separate simultaneous declaration and definitions any more)
(I still think it's outrageous that C is still a single-pass language - we shouldn't need separate simultaneous declaration and definitions any more)