I've been trying to learn it also, but studying alone makes me get bored of it easily. Anyone interested in learning C++ in a group? it'll be so CACHE (lol, get it?)!
It's not much but will give you an idea. Notice that in the benchmarks where the Objective-C programs make significant use of method calling (namely binary-trees and spectral-norm) those programs are at least 2 times slower than the corresponding Java programs.