There are some wonderful UI updates for this release.
Passbook looks interesting, and I really hope it’s something quite automatic. It looks, however, like the company has to manually provide support for. I will find out later today, I suppose.
Facebook integration is a good feature, and will be really popular. I’m interested in the new sharing buttons—a sheet-type dashboard, instead of a list.
The updates to Phone and Notifications are both needed, and very smart. The Accessibility updates are very clever, and well-implemented. The big story, though, is obviously Maps. The tiles look significantly better than those supplied by Google, turn-by-turn looks great, and the Flyover feature is going to be a lot of fun. The automatic traffic delay notification is very clever. I am a bit saddened, though, by the loss of transit directions. It was one of the best features of the Maps application, and one of the most useful things on my phone. Google will be launching their own maps application for the iPhone later this year, and with any luck, it’ll bring that back.
Update: As far as I can tell, developers must create Passbook-enabled apps on their own. As of writing, no supported apps (including those demoed by Apple) are available yet.