As the others have said
PR not serves no usefull purpose, it used to be a main factor in rankings, the better
PR you had the higher up you would go. However, this has been changed and ranking relys on other factors more now.
It can give you an idea of how long the sites been around, and the number of backlinks they have, but thats it.
As I mentioned yesterday in another topic, I have a domain at number 1 in google with PR0, whereas the other 8 results on the page range from PR2 - PR5.