After a long beta period of 6 releases Apple today issued the final version of OS X 10.10.3 where the biggest new feature is the Photos app to replace iPhoto. Photos is closely integrated with iCloud and iOS devices for a shared library of photos if you choose so.
We are seeing better frame rates in some of the viewers with 10.10.3, and the system feels more snappy in general.
The servers will be upgraded over the next few days as also OS X Server 4.1 is expected. Xcode 6.3 was released for download from the App Store with a significant upgrade to the Swift language to version 1.2. Check out the Swift Blog for details.