This is a huge achievement - props to the Gradle maintainers for delivering so much with such careful adherence to backcompat! I’ve had two enableFeaturePreview lines in my repos for a few weeks now and it made upgrading to Gradle 5.0 a zero manual action upgrade!
Backcompat is important, but even better is using the new features Gradle 5.0 ships with, e.g. the production-ready Gradle Kotlin DSL 1.0 which you can convert to (from Apache Groovy) if you want code completion, error highlighting, and simple refactoring when you write your build DSL's.