Don't do it for the Pagerank.
PR can't count on
PR. Do it for the targeted traffic and
SEO results.
It will help. Links within forums, blog comments, blogs and articles do help. Afterall, howelse will Google do it's measurement. Just don't abuse the system, or your client will pay dearly with less
SEO traffic.
A mix of nofollow and dofollow links would be healthy. Too many dofollow links will say something is fishy.
Jut my opinion...