This is kind of an old post, but the SpringSource STS team has released a plugin: http://static.springsource.org/sts/docs/latest/reference/html/gradle/
Installation instructions can be found here: http://static.springsource.org/sts/docs/latest/reference/html/gradle/installation.html
My experience has been pretty positive with it so far. For straight-up Java projects it works quite well. I am having some issues generating correct war files through Eclipse, while using the Gradle plugin, but gradle itself does it wonderfully. I am relatively new to gradle and the plugin though, so it could be something that I am missing.
