While the Grails web site’s front page doesn’t mention it under the Latest News section, Release Candidate 4 is available for download. The release notes state the 85 bug fixes and improvements have been made since Release Candidate 3.
It appears that the team is pushing hard toward a final 1.0 release in the near future. According to Graeme Rocher, the Grails Project Lead, this is the final release candidate before the official 1.0 release.
Also, if you have not checked out the documentation for Grails in a while, you definitely should. Obviously, a lot of attention has been given to the documentation. There is a lot of valuable information there. Give it a go!