The problem with Grails is, like you said, it focuses on getting started quickly, rather then producing a maintainable and performant codebase. I mean, Hibernate is very complex in itself, and adding another layer (GORM) on top of it won't make things better.
If I were to start a new java project, I would probably choose Dropwizard (http://dropwizard.io/), which is more a collection of libraries then a framework.
The business model of the Grails development has always been about integrating various existing software into one branded product for "full-stack" development, such as Groovy and Spring. The Spring and Grails crowds inside Vmware seem to do everything together now (e.g. SpringOne2GX conferences) so I suspect they're now already one group, and that it's the Grails project that's taken over Spring just like they previously took over Groovy.
