I agree with rogerd
I worked with a pet company for quite awhile and we found those top 100 pet sites pulled in quite a bit of traffic although contributed very little to the PR. I think it really comes down to thoroughly researching your industry for all opportunities and then pick the ones that will work best for your niche. With this pet example I found that the folks who were attracted to what we had to offer loved these top 100 sites.
Without getting caught up in link scams or the great no-no link farms and such > I believe itís good to allow some flexibility in your pursuit of linking opportunities and as rogerd suggests > donít forget the potential traffic in the equation.