Writing on The Loop:

The real shining point of Mavericks is the continued integration between OS X and iOS. Whether it’s Maps directions shared to your mobile device or passwords being synced from your iPhone to your Mac, Apple is making their entire ecosystem work for the user.

Apple is really good at releasing extremely well-built versions of OS X. They might not be heavy on flashy features but they make up for it with integration between all of their products and a long list of solid improvements.