Absolutely nothing... with regards to most search engine rankings... Google use nofollow'd links in their algorithm, but Yahoo does. If it is a high traffic PR 7, and a very relevant site, and the link is in a highly visible spot, it can be a great source of traffic. Any link can be good, and it must be a PR 7 for a reason.... Go for it, but don't pay tons.
Yeah, unfortunately links are nofollow for a reason, to not pass on PR. Thats why the majority of the big sites give nofollow links out. May get you some traffic though.
It is worth in terms of traffic. Moreover Yahoo will still consider it as a BL. So, it definately helps.
since it's a nofollow link, its worthless if the site receives so much traffic and you would like to get benefited from the traffic, then tons of blogs out there with tons of traffic allows you to place your links in comment and it's all free, why purchase that kind of links then?
What about that experiment that someone did recently (which I had the citation) where they exclusively used NOFOLLOW links and were able to place terms in the SERP? Has anyone else read that? I thought it was interesting. Made me think that NOFOLLOW was more of a public relations thing than a real rule.
I think nofollow links can pass PR juice. Here is an example. Last week i found this site. Go ahead and check it's backlinks - it has PR 4, and has MOSTLY nofollow backlinks from guestbooks and blog comments. I'd like to hear your opinion.
If you are thinking to get rich traffic it's good, But if you want link juice from it than it's worthless.
I think at one point Google was passing anchor text weight, which may have allowed sites to rank for very low cometitive keywords. However, I believe Google eliminated this - Matt Cutts covered it somewhere in a video, I believe. 99% certain. Good luck finding it... This was apparently not the case as recently as June 25, 2007: http://www.beanstalk-inc.com/blog/2007/06/relnofollow-test-results.html