In my mind, the key differentiator between mediocre events and great events is who the target audience for the event is:

  - A great even is designed for the benefit of the audience.
  - Mediocre events are designed for the benefit of the sponsors or the organizers.

Webstock (http://www.webstock.org.nz/) in particular is great if you're ever in my part of the world. Great signal-to-noise ratio, fantastic speakers, very little of the standard tech conference douche baggery ("10 tips to monetize your blog"; any panel comprised of commentators rather than people who make stuff; etc.) and an upbeat sort of atmosphere that's difficult to articulate.