Conventional wisdom has always been that with all DSLRs the lower the ISO the lower the noise. This test shows that this may not be completely true. For example, on the 5DMKII it appears that ISO 160 has less noise than ISO 100 and that the lowest amount of noise is at ISO multiples of 160. That is, 160, 320, 640, etc.
I haven't tested this on my 5DMKII yet but Fred says he tested both his 5DMKII and 1D MKIV and the he sees the same thing the article is claiming. Also, he was surprised to discover that his 1D MKIV has significantly less noise than his 5DMKII.
This revelation seems to have the biggest potential impact on real estate photographers that are shooting brackets for HDR and Exposure Fusion processing. That's because since HDR and EF processing increase noise in the final image, so you want to start with images that have the lowest possible noise. Maybe you should be shooting brackets at ISO 160 rather than ISO 100. The article suggests that you should test your camera to verify where the lowest noise ISO settings are, don't just assume it's ISO 100 or ISO 160!