SEO is a very complex science. I agree with Chrishirst that actual experience would make you a better judge in determining which works and don't at SEO. I am not an expert nor a newbie as I am continually experimenting on SEO. As per my marketing efforts on our sites, I have concluded that focusing on SERP rather than PR is more viable in drawing the right traffic to our sites
PR IMO works best if you are selling ad spaces, links, etc. - please correct me if I am wrong on this. But then again this is my opinion
Off Topic: Chrishirst, aren't you a MOD also at another forum?