I read up a bit on the features.
Here's an article that goes into greater detail on them. Here are the highlights:
* Notification center (
finally! This will work similar to how it works on iOS 5, and should be a good replacement for Growl)
* Messages (allows the Mac to join in with the IM-style iMessage system that was previously limited to iPhones, iPads, and iPods)
* Airplay mirroring (Airplay is a way to play audio over speakers that weren't connected directly to the computer - this will allow video to be transferred to a television as well as audio)
* Game Center (also from iOS)
* Gatekeeper (security feature - you can set your Mac so that only applications from the App Store can be installed, or so that App Store and signed apps can be installed, or allow anything to be installed. If you have Gatekeeper active, then if Apple discovers that a software author distributed malware, they will disable their key and automatically remove the offending software from all computers)
* Making some apps stand-alone (instead of having To-Do's in Calendar, will now have a Reminders application, same as iOS; instead of having Notes built-in to Mail, will now be a stand-alone application)
There are some rumors about the hardware requirements - it seems like systems from 2007 or 2008 might be out of luck. Shucks!
