Apart from the PR game, strongly positioned links (even nofollow) help you in bringing direct and targeted traffic to your site. I get a great hits on my website from wikipedia, even though it's nofollow.
Nofollow does not matter if you are looking at PR but nofollow links are useful for SERPs as Google is following nofollow links
Thanks for so many replies! Wow! I haven't realized I would cause so much discussion on the topic. So mostly what I would conclude from most of the posts is: - nofollow helps indexing & positioning, doesn't help increasing PR - nofollow is good. Any link is good. Better something than nothing.