The Energy Saver preference has a new addition – Power Nap!
This enables your Mac to check for e-mail, calendar and iCloud updates whilst asleep, which is great, as it saves on syncing time when awaking a machine, the downside however is that it uses more power than the conventional sleep mode, so it’s best to use it only when plugged into the mains.
The Displays preference has changed a bit, with the best feature being the addition of the AirPlay mirroring feature.
If you have an Apple TV then you can mirror your Mac’s Desktop to your TV screen, which is great for simplifying presentations.
You could have an Apple TV hooked up to a Projector or a Large Screen TV, and have people wirelessly connect to them, preventing the messing around with VGA Cables or forgotten adapters.