What you have to realize is that refactoring is a dangerous concept in Objective-C, regardless of which IDE you use, because of Objective-C dynamic nature. Classes can be loaded or switched at runtime, non-existant methods can be called, and class and methods can be variables. Cleanly refactoring is much easier to achieve in a statically-typed language such as Java, which is why Java IDEs are so much better at automatically refactoring.
This doesn't really ring true to my ears. I have some experience with Smalltalk, which is where refactorings were pioneered, and which Objective-C has some roots in. Smalltalk is even more "dynamic" than Objective-C. If you get the chance, I recommend playing around with Squeak or Pharo.
It's not (just) the dynamism of Objective-C that make some refactorings unable to be guaranteed to produce correct results; the "C" part plays a big role as well.
