Groovy's always been good from the very beginning for quick and dirty Java class manipulation, such as test scripts. It found use in Grails when they added a MOP to simulate Rails's ActiveRecord, but Grails is declining quickly -- people aren't starting new projects with it or upgrading to Grails 3.x. Gradle provides it as a configuration language but its typical use is for 30-line build scripts using the declarative DSL only, not the actual language. Gradleware no longer mentions Groovy in any of their promotional blog posts and announcements about Gradle -- it's like they're embarrassed of it -- so I suspect there's changes coming soon in that area.