Android Studio’s biggest feature is not code completion, analysis or even re-factoring - it is the layout previewer allowing to instantly see changest to the layout of applications across different devices in both portrait and landscape mode.
This makes designing applications for Android so much easier so developers will instantly be able to see how apps look and behave on different platforms and should no longer complain about different sorts of fragmentation.
The layout preview is live so that whenever you change the XML in a document, the change is instantly reflected in the layout. You can even edit directly in the layout, but Android warns that this feature is still not completely finalized.
Neatly, those live previews also work for translations making internationalization of your apps so much easier. The new Android Studio IDE is available on Windows, Mac OS X and Linux, and you get start downloading it right now.