I am an old user of IntelliJ but new Grails. I am very much enjoying the Beta of the JetBrain Groovy&Grails plugin.
However, it has a fairly annoying bug that should be fixed before V1.0-- dependencies don't work.
If you Grails project depends on libraries or Java from other modules, the IntelliJ won't complain, but the .jar and .classes are not deployed and the application fails at run time.
Please feel free to move this, if there is a better place to report bugs.