I'm a full time java developer but use rails for my hobby projects. We evaluated grails for a project at work a year back. My experience with grails left me feeling a bit disappointed and this was the reason that I began to investigate rails. Having used both my impression is that even though groovy is not far behind ruby as a language, rails provides a significantly improved experience over grails. Quite simply, rails seems to solve far more real world problems, particularly when you factor in the number of good gems that are available. I'm thinking of things like, providing search, versioning, rss, non crud apps, integration with cloud services, etc.
I get the impression that grails is around about the level of rails 1.x. By the end of this month rails 3 should have been released. We've actually decided to now move towards using rails at work. In the end, grails is easier to pick up for java developers, but ultimately lacks the refinement to cover a wider range of project requirements.
