I wish there was an easy answer.
Since only the engineers in charge of assesing quality of links for Google know for sure - we're just guessing what happens when Google sees a link has the "nofollow" attribute attached.
Me personally - I will not go out of my way to get a link if it is nofollow - I won't pass up the link - but my guess is it counts for very little if anything if Google sees the nofollow attribute.
Now - we should remember that in the real world that successful web sites have all kinds of links - some of them are surely nofollow - so my guess is it's quite normal to have some of your links be nofollow. We do want to be NORMAL! NOW if they see TOO MANY links are nofollow I bet they will PENALIZE the site getting the links because it is very likely they are doing some kind of comment spam linking.
As far as Bing goes - I bet they ignore the nofollow - but who cares about Bing?