PR for PR's sake is useless, I can outrank any PR 8 site with a PR 5 just get tons more backlinks with appropriate anchor text and low Pr. PR does not help rankings at all, the link volume and the anchor text used is what helps your ranks.

What Pr does do is increase your spider visits, encourages the spiders to go deeper etc, however thats not what I use buying PR for.

When I get a new client, right away I buy them PR, WHY? Because for some reason the rest of the world hasnt caught up to the SEO Expert I guess lol so they wont exchange links with you unless your high PR. So my solution is to build up a site to say circa PR 7 and then guess what 95% success rate on emailing link partners, long term stable links, many IPS many sites many anchors etc.

Eventually I ween the Pr budget off and we still have all those nice juicy links. Thanks Guys!