It is definitely worth it, provided the links are free of the nofollow tag. Contrary to popular belief, nofollow links have no benefit, not even for making your link profile look more natural. It doesn't work that way as nofollow denotes user generated, vulnerable-to-spam content. Couldn't resist.
You should start to see your site rise after you get high PR comment links. Note, however, that the high PR score has to be on the page you leave the link. The PR of the home domain has little impact, if any.
If there's an OBL count (outbound link) of 200 or even more, I would say it's still worthwhile leaving a link on high PR pages.