To learn more about Groovy, you can read the InfoQ article on the new features of Groovy 1.5, and if you are beginning with Groovy, a first article will introduce a Java developer to Groovy in a few easy steps -- more articles of this kind will follow.
Groovy, the dynamic language for the JVM, is being used in various sectors from the health sector, to the financial sector, in mission-critical applications dealing with checking and improving patient files or handling millions of dollars of investments in hedge funds. As the saying goes, in French, Groovy matures like good wine, and this release helps ensure the quality standards are met.
In parallel to the 1.5.x branch, G2One and the Groovy developers are working on the upcoming 1.6 version of the language. A big focus is being put on performance improvements, to make sure Groovy is ahead of the pack. Some advanced call site caching techniques are being applied to gain every bit of performance that it is possible to get with the current architecture of the project.
Groovy has long suffered from the showstopper of the lack of good IDE support. Fortunately, with the very advanced IntelliJ IDEA Groovy and Grails plugin, you get the same level of support you'd expect from you Java IDE: syntax highlighting, semantic analysis, quick fixes, unit testing integration, code completion, and even refactorings! But this is not all: the Groovy Eclipse team released a brand new version of the Eclipse plugin that is compatible with Groovy 1.5, and Sun is currently working on its Groovy and Grails support in NetBeans.