Upload & Sell: Off
Should you get a 5DmkIII? I don't own one but I'd like to share some thoughts that might help you decide.
I've owned a 5D for 7 years and 6 months ago I bought a used 5DmkII. In the first 6 months of 2012 I've wondered and wondered about what camera I should get because it seemed so utterly important to my photography. Now that I've used the 5DmkII for some time I know that it will do fine for 95% of my photography. And it only cost me 1100 Euros, it had 14000 actuations when I bought it. I now shoot my trusted 5D and my "new" 5DmkII.
After 25 years of amateur photography I decided to start a business recently. I own about 4 good Canon lenses and now two bodies. I feel that most of my misses (which aren't many) are user error and only some could have been prevented by a better camera body. And in my line of work that is not that significant. I shoot studio portraits, bring my studio on location for portraits, shoot for businesses, some product photography and some theatre work. And it's only the theatre stuff that make me wish I had a better AF body sometimes. But I don't do enough theatre work to benefit from a 2800 Euro camera body.
So basically I am quite satisfied with my 5D and 5DmkII, where formerly I thought I'd really really need a 5DmkIII. Seeing things from a business investment perspective makes me look at gear acquisition much more rational than before. Do I really need a better camera body? Will my business benefit from the investment? At this point, no.
Will your photography benefit according to the price you pay for a 5DmkIII? Not very likely, but certainly possible. I'm sure you will like it better than a 5DmkII or 5D. Whether you feel it's worth the cash will depend on the amount of cash you can spend on this stuff.
There is one area of photography that I would like to explore a lot more and that is wedding photography. I have this incling that if I'm successful in this field and start doing it more, that I will end up with a pair of 5D3's. AF with even the most challenging lenses to focus (like the 50L and 85L), quiet mirror slap and dual card slots will probably convince me to buy. But if my business stays away from frequent weddings, I'll stick with what I have now.
Hope this helps.