I don't agree .. Yes, Pr isn't an important factor for ranking (and so for getting traffic) , but it's important for advertisements , for getting quality links to your other websites etc etc ..
I hate this tired old debate..why not get a high PR rank while you focus on content? When you sell websites, people ask for PR all the time.
the thing that says "pr is important for advertising" it's not ok you can do 3 sales for advert spots with your pr but if you have high traffic you'll be happy with the earnings from adsense,etc. and wouldn't want to sell adverts any more
PR is not important compared to traffic and sales BUT if you are a high PR rank because you have top websites backlinking you most importantly goverment/institutional websites then its very important.
Is important in one way Traffic> earnings, but you haven`t any high cpc if you have PR on a site using adsense