I was researching fast enumeration, very efficient BTW, and stumbled across this article, about bypassing dispatching when making calls during enumeration. It could also apply to high frequency dispatching. You basically grab the method address and bypass dynamic dispatching.

http://www.formconstant.net/diagrams/?p=40&preview=true

void (*doSomething)(id, SEL);
SEL doSomethingSel = @selector(doSomething);
doSomething = (void (*)(id, SEL))[MyNSObject instanceMethodForSelector:doSomethingSel];

for(MyNSObject *obj in nsArray) {
   doSomething(obj, doSomethingSel);
 }