Originally Posted by peach

Like I posted in this other thread, pagerank is the the reverse logarithmic approximation of the actual value that google assigns to the link power of your pages.
If you take in regard the side-effects of hilltop-like algorithms and spam filters you can use even the approximated toolbar pagerank to get a good idea of the link power of your pages, or your competitors pages if you research their backlinks.

So in order to determine the value of your pagerank 6 you have to research where it came from, how relevent those sites are to yours and how much link power those sites have.