Groovy keeps growing tremendously. Second most popular number on the JVM after Java. 1st quarter 2018 twice number of download vs 1st quarter 2017.
In the presentation, Paul covers some of the features in 2.5 such as the new AST transforms, improvements in previous transforms, new methods, Macros support ... and the improvements coming in 3.0. I love that 3.0 brings as close as possible interoperability with Java (Lambda support, Java-style array initialization etc).
Checkout the Slides.