According to dxo labs the 1dsIII has about 12 stops of dynamic range, the Nikon d3x has an amazing 13.7 both at iso 100. If its near 14 stops like the Nikon flagship with low noise that would be amazing for wedding and landscape photographers.
I believe even Nikon's 16 MP APS-C cameras like the D7000 achieve 13.9 eV of dynamic range (so much for all the myths about larger pixel size giving wider dynamic range), beating out their very own venerated 12 MP FF D3s which has 12 eV of dynamic range. Canon's Archille's heel really lies in their sensor electronics. We'll wait for real world tests to see if they have overcome this.
Dxomark's dynamic range measurement is actually quite useless and confuses many. What they measure is the mathematical/engineering type of dynamic range, how small a signal can be until it is equal size as the noise. That is not the same as saying that shadows 13.9 stops down are usable to the photographers, when the signal is equally large as the noise there is not a usable picture! The measurement does not say anything about how much dynamic range that is useful in a picture, well only that it is considerably less than 13.9 stops. Typical usable range in a good digital camera is around 7 stops if I remember correctly -- the reason why it so much smaller than the measured dynamic range is that you must have much more signal than noise in your shadows for a picture to be pleasing.
It is better to look at their SNR 18% measurement, which shows how much noise there is in parts that are not insanely dark, and there you can see for example that the 5D mk2 has less noise than D7000, despite that its "dynamic range" is only 11.9.
But then there's another factor -- pattern noise -- which Canon happens to have problem with, meaning that you can see a pattern in the noise. This is not measured by DxOmark, but does reduce the useful dynamic range, because most people really don't want to push the shadows such that you start seeing noise pattern. Noise that is totally random is much more pleasing to the eye.
And there's yet another factor -- auto exposure -- if you let the camera expose the picture itself it may play it safe and leave space at the top to avoid clip highlights, or it may push the histogram as far to the right as it can. If I remember correctly the D7000 autoexposure exposes much farther to the right than for example 7D. This means that D7000 will seem to have more dynamic range than it actually has. When you expose manually you can max out the sensor as you like.
In all, useful dynamic range is subjective and need to be tested, it is not easily measured.