In the last year or two, there has been a veritable explosion in the number of Grails plugins out there. Without proper testing, however, they run the risk of falling into disuse as users avoid them.
Grails plugin testing
Peter is a long time Java developer and one of the core Grails committers. He has been developing with Grails since version 0.2 (give or take 0.1). He created the GWT Grails plugin as an exercise to see whether it was possible, but it has since grown into something that can support serious development.