Here is a link to a very interesting Flex on Grails book.
In researching our next platform, I'm impressed with Grails. Grails seems to create a platform where applications are developed with few lines of code, they use very efficient components (i.e. groovy), and the focus is on a high quality applicaiton built on industry best practices.
As we extend our UI from Notes, we will take advantage of both Grails and Groovy.