Apparently I'm a huge fan of Will, as I also made notes of his second talk about Akonadi and pimping PIM. It's rather unfortunate some guys who were interested in his talk didn't come, but at least I enjoyed it.
Starting with the history of KDE PIM, he explained how the hackers want to go from a very monolithic infrastructure in KDE 3 to a much more modular and flexible system in KDE 4. Akonadi will be that new infrastructure. The way KDE 3 handled data wasn't scalable, and in these days of huge social networks and all kinds of online and offline data you need something which can adapt to any new kind of information easilly. Something which can be used by the whole free desktop - a clean seperation of UI and data, caching, sharing and easy synchronisation. Akonadi will make it easier for application developers to access and combine data, thus allowing new and innovative uses of knowledge and information on the Free Desktop.
Further Will went into some more specific details of the Akonadi design, explaining the choices which were made. For example, they choose to use IMAP as the main protocol for the movement of data instead of DBUS mostly for efficiency reasons - DBUS is used for controlling the Akonadi server, though. Akonadi is entirely type independent, and features a smart cache for remote data with change notification and conflict detection. So, you can store anything you want, work offline with your data, your applications are always up-to-date and Akonadi also ensures the integrity of your data.
And of course - as Akonadi will be here soon, Will gave some pointers about how to use it and the roadmap for the future. There is a developer preview available, so it's time to start having a look now... The Akonadi developers are looking for someone willing to write glib/gtk bindings so the cross-desktop part can get started, and of course there are many other things which could be written. One can clearly see Akonadi fits in the KDE strategy of enabling more innovation and thus serving the Future of the Free Desktop. I can only say 'great job' to the KDE PIM developers!