One theory is to use the high PR that your main page has and channel that to only the important pages that you want to give the most PR benefit to, and those pages you don’t care about, eg contact details etc, don’t link from the main page. That way you are not diluting the PR to pages that may be necessary but aren’t important in the selling process for SE traffic.
BUT, don’t let SEO win over usability. Make it difficult for the visitor to move around and it doesn’t matter how much traffic you get, if they don’t move past the first page and leave your site then all the SEO in the world is not going to help.