How Healthy is Grails?
One question we get a lot at Cantina is that of whether Grails is a passing fad, or if it is something that has some staying power. We have gotten that question (in some form or another) quite a bit, so it might help to explain where we’re coming from.
I agree with Adam’s thoughts in his previous post and have been very impressed with the activity in the Grails community. I subscribed to the user mailing list. Each day I receive from this list anywhere from 40-60 emails from users running into various issues on projects and folks from the Grails community providing their suggestions or troubleshooting tips. The activity of user/developer mailing lists is one of the most important benchmarks in determining the health of an open source framework - along with supplied functionality (obvious), core technology, the architects driving the vision, commercial support, documentation, check-in velocity and discussion in the blogosphere. To give an indication of the acceleration of activity in the Grails community, in October 2006 the same mailing list was averaging around 5-6 emails - almost a 10 fold increase in one year.***
Also, last week on the Grails user mailing list, there was some spirited debate on the level of Grails documentation (or lack of it) and whether it was appropriate for the release level of the framework. The amount of documentation right now doesn’t really concern me. What struck me the most about the dialog was the intensity of the debate. It shows the community is excited about what has been developed, are passionate to help out in whatever way they can, and care deeply about the frameworks success. And the community’s passion/enthusiasm for Groovy/Grails is clearly indicative of the framework’s ability to meet a need and fill a gap, something the community is looking for. IMHO this enthusiasm will be the driving force of success and perpetuate Grail’s momentum. And while more formal documentation is sure to come down the road, I’ve found the answer to most of the issues i’ve run into by querying the mailing list. It has been an excellent source of living documentation. - http://www.nabble.com/codehaus—grails-f11860.html
Of course with every new open source project there is always a lot of user/developer mailing list activity in the beginning. The question always becomes: Does this activity last, does it have staying power? With over a year and half of Grails development under their belt, a pending 1.0 release, and the clear need for a rapid application development framework in the J2EE architecture landscape, I have the feeling Grails is here to stay. Now I’m just trying to find the best way to support the growth… 
That being said, one of our goals here at Cantina will be to leave some tips/issues that we run into as we develop plugins for the framework. Although it will not be formal documentation - we get our kicks from developing functionality - there may be some issue/tips that we run into that can be helpful to you. And please feel free to weigh in by leaving a comment if you know a better approach.
*** fyi, this calculation was performed with a VERY informal last year inspection of the mailing list on Nabble
UPDATE - 10/31/2007
I guess I should be been paying attention to the email threads a little better… Two email threads -
http://www.nabble.com/number-of-people-companies-using-Grails-tf4721318.html
and
http://www.nabble.com/Mailing-lists-statistics-tf4693805.html#a13416495
also discuss the growing activity of the mailing list.