If you have contributed in some way to free software (i.e. if you feel you can get certified to at least Apprentice level), the answer is yes. If you just use free software, then an account won't really help you that much.
The main thing an Advogato account does for you, is give you a point of reference on a major free software community website. You will immediately be able to create a profile page and a blog. Once your account has been certified by other trusted users, you will also be able to post to the news flow, create projects, or syndicate your blog to the Advogato recentlog from your existing blogging site. Trusted users also get an RSS feed for their blog and an autogenerated FOAF RDF file for their profile. New features are being added all the time, so being certified will bring other benefits down the line.
Oh, and did we mention that it's fun? So if you are a free software developer, go ahead and sign up.
Attention spammers: It may seem like creating fake accounts for spamming search engines is a good idea. Seriously, It's not. All links you create will automatically have the nofollow attribute added to prevent them from being picked up by search engines. And every account you create will be deleted within hours anyway by our community spam control system. Save yourself some wasted time and effort - move along.