Yes, more REST style would be nice.
Recently i stumbled upon the Restlet Framework (http://www.restlet.org), which I believe is extremely slick!!
I don't know how far it is possible to integrate all the features into Grails, but maybe at least one thing you could do:
The current GrailsController has a "request"- and "response"-attribute which uses the HTTPServletRequest and -Response.
It would be great, if Grails would use the restlet.Request and restlet.Response, because they are easier to use and more natural imho.
Keep up the great work, and thanks for bringing all the Rails Goodies to the Java world.