If you think the only reason to go to a conference like ZendCon is for the main speaker list, you're missing out on half the fun and content. The Unconference, managed this year by Keith Casey promises to be one of the best ever (here's the list of suggested sessions so far). Matthew Weier O'Phinney agrees and in his latest post he talks about why unconferences are important and why you should attend.
Why should you care? There are great sessions already selected for the conference featuring some well-known speakers from the PHP world; why would you want to either attend or present at the uncon?
He talks about how the unconference atmosphere can help with continuing the conversation from other sessions (like a subversion talk that spawned off a best practices session), how it can be a "springboard" to getting into the speaking world and how it can help to explore new ideas and concepts that the main conference tracks just don't make very easy.