Only you know the answer to questions like this.
Is it worth it? Well, that depends on what you want. If you feel you need the better AF then it may well be. If you do mostly studio work, then a 5DII will probably be almost as good at a much lower price.
The answer also depends on your available leisure money. If you earn $30k a year, then you would probably be better served saving some money for something else. If you earn $300k a year, then you probably won't notice the extra cost of the mk III.
Look at the features, weigh up what will actually be of use to you in the features you only get on the mk III, then consider what else you could get with the same money instead, a new lens perhaps, and would that be of more use than a slightly better body.
We can't tell you if a mk III is worth it to you, only you can decide that. I am currently trying to decide between a mk II plus something else, or a mk III, but whatever I decide upon will be the best option for me, it may not be the best option for you.