Yuri Arcurs did an interesting review comparing the Canon 1Ds Mk III with Nikon D3X for the purpose of stock photography. Comparing image quality, lens sharpness as well as handling, he found the Nikon more suited for his purpose, even though Canon's noise management is better than Nikon's. Find out more details at his blog.
In response to Rob Galbraith 's query regarding the D3X sensor, Nikon acknowledges that it was manufactured by Sony but has a "unique sensor design" that was "developed expressly for the D3X." The full response on Rob's site is as follows:
The Nikon D3X’s 24.5-megapixel FX-format (35.9 x
24.0mm) CMOS sensor was developed expressly for the D3X in accordance
with Nikon’s stringent engineering requirements and performance
standards, with final production executed by Sony. Featuring refined
low-noise characteristics, 12 and 14 bit output, Live View capability
and more, the D3X’s unique sensor design was carefully blueprinted to
perform in perfect concert with proprietary Nikon technologies
including EXPEED Image Processing and the Scene Recognition System.
Meticulous efforts allowed the sensor to become one of the many
essential components and technologies which contribute to the D3X’s
superior image fidelity.
Whether the sensor is indeed different from that of Sony we would have to wait for more tests. Stay tune!