Although the graphs are available anymore as I ran out of space in my gallery, I summarised my views on the camera noise comparisons based on the measurement work of DxOMark in
this thread.
If anyone is interested, I have a PDF of the article I can email out with all the graphs.
For me, the bottom line is:
The Nikon D3 (and D700) is king of the hill when it comes to noise. Before that camera came along, the Canon's offered significantly better performance and that was generally acknowledged. One of the reasons the D3 is seen as so good is that its predecessor, the D2X was so poor.
The reason the D3 is so good is partly it is a modern design sensor but also that it has the biggest pixels of any non MF SLR camera as it is 12Mpx on a full frame body.