Because of the delay with it's backlink's update period Google have managed to control the link broker's pagerank eventure.
Many would say that analyzing Google's backlinks is close to worthless, but still you need to know if your partners have your backlink with your keyword hostet on a good PR page.
Pagerank still have some importants and link's poiting to your homepage is a part of the algoritme and relevant to some extend. You will never know the exact number of backlink, and they would be different from search ingine to search ingine.
Link building campaigns can be time consuming, and you will never be able to guess the effect on the pagerank result. The best link would be thoose coming out of the blue, from peoble who decided your content is important and give you a link.
In the end I think it's thoose kind of link that make the difference between PR 5 and PR 6,7,8,9,10 and off cause traffic. Content is king and SEO is the throne.
Kim Anton Hollenner