Sure. You still get back links if you reply to a blog post. You still get human visitors who are going to see and click.
If you're interested in getting back links for pure search engine purposes, then the answer is the yes and no. Yes if you comment on blogs that don't use nofollow. No, if you comment on blogs that use nofollow.
Many bloggers are adopting the "Nofollow Free" notices. That is, if they don't use Nofollow, they may place a logo or small note saying so. There's a list of WordPress plugins that remove the NoFollow tags from comment links: http://andybeard.eu/2007/02/ultimate...rackbacks.html
There's a list of social networking sites that don't make use of nofollow: http://www.searchenginejournal.com/s...-engines/5985/
There's also a list of blogs that don't use nofollow, published on the blog of my friend, Courtney Tuttle. http://courtneytuttle.com/blogs-that-follow/
Hope that helps!