my issue with objective-c and its runtime is the message passing implementation and the reliance on it - it is incredibly powerful, but the cost is phenomenal in the contexts i work with - and a common optimisation i find myself doing is making C++ style calls out of c functions with a 'this' as the first parameter.

there is no real need for this cost if the compiler could have more information about use and respected the "don't pay for what you don't need"