If the website you are getting the link from is a high quality website then don't worry about whether or not the link is nofollow.
You shouldn't spend too much time overanalyzing whether one particular link is beneficial. Here is one way to look at it: If the people who visit that web page are in your target audience, then that link is beneficial. You have a chance to spread your name, get traffic, introduce your site, whatever. Not every link has to be about pushing your ranking higher.
If ranking higher is the only thing you are worried about, then you probably don't have a website that is worthy of ranking at all. Just go get the links and don't overanalyze things. Try to avoid spamming in the process.