Re: Objective C
Put simply, it's worth it if you aim to make stuff for the mac. That is the only reason why it's worth it though, for all intents and purposes it was a horrible choice of language from apple (I only assume it's because they hate developers!) and pretty much any other popular language out there would have been a better choice.
I looked at it briefly a while back, and after looking over the details concluded that I just couldn't be bothered to write stuff for mac platforms!
Save the whales, feed the hungry, free the mallocs.