No follow links don't add any value to your website. It doesn't effect your traffic stats and ignores the backlinks pointing to your site. However, you shouldn't completely avoid it. Google knows that sites that are using blackhat methods will have no nofollow links. If a site has no nofollow links, they will get penalized. That's why you need a specific percentage of nofollow links, I heard around 16-24% is the average, and anything mroe than that is fine. Anything below 16% triggers Google's red flags, so you should be careful for that.