Groovy released version 1.5.6, so making a Gant release was something to think about. People had been using 1.2.0-SNAPSHOT for a while and there appear to be no problems. All in all it seemed right to shift from 1.1.x to 1.2.x -- there are some breaking changes as well as lots of new goodies and some important bug fixes.
As ever distributions are available at http://dist.codehaus.org/gant. For those who use Maven 2, the repository URL is http://repository.codehaus.org, the groupId is org.codehaus.gant, the artifactId is gant , and the version is 1.2.0.
The Gant webpage has the documentation.