Links within PR’s won't help SEO directly
Google's Matt Cutts announced late last year that an age old SEO tactic of placing links within PR's and doing widespread distribution will no longer directly impact an SEO campaign. The theory being that the tactic itself generates a large amount of duplicate content and low value links which these days could hinder a campaign.
SEO agency SEO Consult tried to disprove this by releasing a PR through PR.com with a link to Matt Cutts blog using the anchortext "sreppleasers" - a susposed anagram of Press Release (although they messed this up by using an extra "P" and missing an "E"). The test itself did show signs of being a success, with Matt Cutt's blog starting to rank for the keyword, but the result soon began to fall within the rankings meaning that it only received a temporary boost.
This news does not mean that online PR is not worth the hassle as if the release is of high quality and contains real news there is still a chance of obtaining a link from a national newspaper which will provide a direct boost to your SEO campaign.