The update can be installed via Software Update on your Mac. Apple says "This update is recommended for all users." It's should also b available on the Mac Dev Center shortly.
If you aren't a developer and you want to test the new operating system you can register here.
Apple also seeded the third beta of iOS 8 today to developers for testing.
We are updating shortly, so stay tuned via Twitter, Facebook, Google+, or RSS to find out what's new!