This post is similar to http://jetbrains.net/devnet/message/5208587, but I think it's worthy of its own thread.
I use Grails pretty extensively within our company across a number of projects; the IDEA support is really great, especially in 9.0.
One general Grails (not IDEA) kink we have is that the default 'grails.work.dir' (/home/myaccount/.grails) isn't feasible for us. A couple of reasons: (1) if your local project directory has a name like 'trunk', then Grails will create a '.grails/projects/trunk directory.' Fine if one app does it, but bad when 10 apps do it, especially when you're trying to run more than one at a time. (2) Some of our machines don't have enough space under /home for all of the dependency jars, etc.
So, I've overridden 'grails.work.dir' in all of our projects to use a 'work' subdirectory under the current project. Any ideas about how to make IDEA pick up this setting and look for dependencies in the overridden location? Admittedly, I haven't tried to work with the PSI at all yet.