Maps includes a lot of great new features, including 3D buildings, turn-by-turn navigation, local search with some back-up from Siri. Maps also includes live traffic information that's anonymously crowd-sourced from iPhone and iPad owners. The live traffic data will also update your estimated time of arrival as you progress on your journey. Your navigation view will also show on the lock screen which is really nice. Asking your iPhone "are we there yet?" will even work through Siri, but you'll likely be spending more time using Siri for local search, such as to find the nearest gas station.
Our WWDC liveblog has it all! Check out the rest of the announcements there!