I've also heard a little bit more. First of all, iOS 6, which is expected to be shown off in developer preview form at WWDC in June, is internally codenamed "Sundance". Second, while Paczkowski's source said the new maps functionality will "blow your head off", I've been told that's a bit of hyperbole (you think?). Specifically, while the 3D functionality is cool, it's also not something people are going to use regularly. Think of it like Google Street View — cool, but how often do you actually use it when compared to the regular Google Maps product?
Other goodies: rumours of Siri for iPad in development, iTunes 11, and third party Siri APIs, which Daring Fireball also mentions.
Clever inter-application communication. Seems crazy that iOS, the direct descendant of NeXT, doesn't have anything like Services, which were one of NeXT's most touted features (and rightfully so). It's also worth noting that Android has a pretty good Services-esque system in place, called "Intents", and Windows 8 has an even richer concept called "Contracts".
Third-party Notification Center widgets. Like the Stocks and Weather ones from Apple — information at a glance, without launching an app.
Third-party Siri APIs. Let other apps provide features you can interact with through Siri.
What do you want Apple to implement into iOS 6?