Maps in OS X was expected, but is very welcome. After a rough beginning on iOS, Apple Maps has been progressing, and now with Maps running on OS X, we'll see some powerful integration between the Mac and iOS. Maps on a Mac looks smooth and impressive in 3D.
Even better, there's a big effort to integrate maps with Calendar, and sync mapping data between all your Apple devices. If you set up an appointment, you'll get the ability to map it, and when scheduling your day, the travel time and traffic will be taken into account. Also, Apple says you can send directions from your iPhone to your desktop, or back the other way. Sent directions will show up as notifications, so it is easy to start on your journey without a lot of fiddling around.