One little suggestion, I can't see anything of your network when I visit the main page. I'm hesitant to sign up for something if I can't see it. Maybe you could add a list of users of the instance / network, public tweets, etc. Or even better, publish a link to a (public) profile, so users can get an idea what it looks like in use.
(If I'd make a federated microblogging / social network site, I would center it around the profile page. I'd make it at first glance less about networking and more about presenting yourself. Like the early Facebook, or MySpace. This way, a user has an incentive to sign up even if no or only few friends are on the network yet. You'd be able to customize your page a lot, leave contact data, write (micro) blog posts, have a wall (guestbook) etc... And almost incidentally you'd be able to use your identity to comment on GNUSocial, use XMPP, OpenID, ....)