After announcement of Android N, Google officially launching Jack toolchain with Android Studios 2.1.
The main advantages of Jack (due to this page) are:
Completely open source
Available in AOSP; partners are welcome to contribute.
Speeds compilation time
Jack has specific supports to reduce compilation time: pre-dexing, incremental compilation and a Jack compilation server.
Handles shrinking, obfuscation, repackaging and multidex
Using a separate package such as ProGuard is no longer necessary.
But annotation processing, code weaving (e.g. aspectj) , bytecode manipulation are not supported (which are really important for me).
Also speeds compilation time was not sensible for me, I created a sample project with a little bunch of dependencies and in both jack and default compiler, the compile and build time was less than 10-15 seconds.
So Why do I migrate to Jack?
Now with Android Gradle Plugin version 2.2.0-alpha1 or higher, annotation processing is supported by default.
Also due to this issue transform API, which is useful for bytecode weaving, will be supported later.