There are no major improvements to the IDE; Google just made it stable enough to take the ‘beta’ tag off of it.
It still has a lot under the hood developers should be excited about, though. Android Studio’s emulator is lightning fast, and shows you the effect changes to your code will have on the end product in real-time.
There’s also the Cloud Test Lab, which lets developers test their code on a variety of cloud-based emulators that mimic actual Android hardware. You can choose different devices along with various configurations to make sure apps run as they should.
For Android developers, Android Studio is basically the best IDE there is. It ties into Google Play and search (via app indexing) intrinsically, leaving little to do but write the actual code (which may someday be Swift).