Well, I agree the AF of the 5D3 might be better than the Nikon, but don't forget that Canon was way behind in this domain till now, the 5D2 AF is simply a shame, it was time to correct it.
The same way Nikon was late with sensors, they improved dramatically here.
Don't misunderstand me here, the 5D3 would have had a sensor in the 28-32MP range, I would have bought it immediately, I'm glad Canon has finally developed a decent AF (though of little concern for me, since I focus manually most of the time), I am just disappointed they could not release such a sensor after 4 years, I don't care too much about high ISO so for me the 5D2 will do the job a bit longer.
What is more bothering me is the metering system, with or without flash that allows Nikon owners to use auto modes without even thinking about it (since the F801), Canon still has some work to do here. Once again, little concern for me since I use manual mode and studio flashes, but still a useful feature for quick outdoor shots.
The features I rave the most about the 5D is the 100% viewfinder and the integrated level, but still 3.5k is a bit too much for these features alone.
What I am just saying is that everyone is drooling when a smartphone has more pixels on it's screen, or that compact cameras are in the 18mpx range nowadays, but no one seems to find funny that a brand like Canon could not improve the resolution of its pro cameras in 4 years.
I am not complaining about the improvements on the 5D3, I am honestly criticizing the lack of novelty about the sensor, that barely evolved in 4 years, when Canon was the absolute leader in full frame sensors till now, it just seems they stopped on their way. One could have expected a camera not only with a better AF and light metering but AS WELL a better sensor.
Let them release the same camera with a 30+ mpx sensor, I'll be first to buy it, my personal opinion is the 5D3 offers little image quality improvement (aside from the high ISO) and it's a bit overpriced for what it has to offer.
I would gladly stay with Canon, just for the TS-E lenses that are irreplaceable for me; speaking of lenses and accessories, a little effort on the prices would be welcome as well, price increase has been a bit surrealistic these last years.
Once again I am not a fanboy of any brand, I just try to keep an honest critical point of view, even about the tools I use, since perfection is not part of this world.
I am just hoping that this healthy competition will lead Canon to release the big mpx sensor a lot of people are waiting for...