The PDC was a little different last year. It was held on the Microsoft Campus, meaning that only a thousand people could attend, when usually it's 5 times that. But it featured an amazing player that opened the whole conference up to the world. I was one of the 100,000 (yes, 100,000!) who watched online. If you are interested in some of the technical details, there's been a whitepaper released. You can read about it
on the Windows Azure Team Blog. Makes sense, since Azure was a big part of the solution.