This sounds great but I'm not sure what "an unconference format" means in this context. Is the idea to carve out a day, and a number of rooms, for attendees to congregate and build their own schedule of talks and BoFs to deliver on that day? Presumably there would be a grid for attendees to propose talks and then people can just turn up to whatever took their fancy? I'd be very keen on such a format!

Andy, yes, this is exactly what we mean by the "Unconference Format".

The unconference virtual grid is live Andy. Check out websphere.uservoice.com . Feedback welcome. Bring your ideas and vote up the ones you want to attend. We'll also have a live paper grid on the wall during the conference. We'll have over a dozen rooms reserved for Impact day 4.