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Human and chimps have 99+% identity in the coding regions of the DNA. Overall they are 98% identical. The difference is in non-coding regions - area that are increasingly being shown to be involved in regulation of development.
So, what do you mean by "considerable genetic differentiation"?
I think what I meant was:
"But the results of a new study call that figure into question, with a finding that there are actually large chunks of the human and chimp genomes that are vastly different.
Researchers at a company called Perlegen Sciences in Mountain View, California, used a powerful biological computer chip that can scan the entire genetic makeup of an organism, that is, its whole genome. The results, published in Monday's issue of Genome Research, show that chimps and humans are much more different than scientists previously thought. "
This means that 99% figure you cite is incorrect.
There are considerable genetic differences between primates and humans according to this study.