I want to point out to two more considerations, memory usage and job market. Grails application takes a lot of memory especially in development mode e.g. 600 Mb for a medium sized application. When deployed in production mode, e.g. war file in Tomcat, the usage can be about 500 Mb. This is partly inherited from using Java.
As for job market and as far as I have read, there is little demand for Grails programmers in job vacancy announcements compared to e.g. Django and Ruby on Rails.
