This is the first beta release in the 3.0.0 release line. It consists of 576 bug fixes, improvements, and other enhancements since 3.0.0-alpha4. This is planned to be the final alpha release, with the next release being 3.0.0 GA.
Please note that beta releases are API stable but come with no guarantees of quality, and are not intended for production use.
Users are encouraged to read the overview of major changes coming in 3.0.0. The beta1 release notes and changelog detail the changes since 3.0.0-alpha4.
2017 Oct 3