It does not fully support C++11. For instance, I still get squiggly underlines for brace initializers in 2.6.2. Renaming is very unreliable. Code navigation doesn't recognize the standard library that's actually used according to the .pro file. Every compile gives me spurious warnings about missing directories on the Mac.

And the documentation is awful. I still haven't figured out how to make precompiled headers work with clang (but that may be my fault).