The lack of a built-in profiler was a big one for me (though this may have improved recently). I do like using external tools like Intel VTune or Morgan Stanley

The lack of a built-in profiler was a big one for me (though this may have improved recently). I do like using external tools like Intel VTune or Morgan Stanley's XPedite but they're not great for the "quick profiling" you might do to test out various implementations of a function or component. Maybe that's been added since I used it 1.5 years or so ago though.