The problem with the TBPR, which I run into on a daily basis is when I am running link building, is that the focus tends to end up only on PR.
I have had link-builders say "we have gotten 10 PR5 links bla bla bla..." but the links tend to be of little or no value because of non-related content or a gazillion other links on the page to bad neighborhoods.
I tend to focus on other parameters more strongly than the TBPR. I would, for example be happy to get a link from a page with TBPR0 - if the other signals I check for provide value.
I'm not saying don't look at TBPR, I do use it for some analysis. I am saying however that if your linking pitch is "this is a PR4 website" ... well then good luck with that.