I have a slightly different view: Nofollow links are not completely useless. I had a site which i wanted to just use for testing purpose. I basically gave it only nofollow linkbacks. After a period of 30 days it started to reflect on the google search engine and by 45 days or so, i got one of my keywords to the top of the google search. So, what i'm trying to say here is that it not completely useless like most of them have mentioned here. Its just that it helps in indexing by not as good as dofollow links. So, dont be biased and do comment...
Well no follow is prevailent on wikipedia for example and as such Google has said that having a link there does not affect your ranking or get you higher ranked or anything of the sorts. In the end what matters is quality content coupled with good links pointing to your site that are great.
NoFollow links don't count for PR purposes but they can pass trust and help your site get index faster (e.g Wikipedia links) About link sculpting - Google claims that you can no longer use NoFollow in this manner because it will not increase the weight that is passed to the dofollow links. I wouldn't go and remove old nofollow links since it can cause many problems but i don't think new sites/pages should employ this method for link sculpting.