PR is overrated and not a ranking factor by google or any other search engine. You want to focus on links, searchability, keywords and things that drive traffic to your site.
PR is like an extra straw in a McDonalds Bag. You get excited for a second and say "Hey, they gave me an extra straw!" but after a few seconds that fades as really it's of little to no use to you!
Focus on quality links and quality traffic - PR increases automatically, but is really just an aftereffect that is not used by search engines to rank your site.