I'll share my 3-years experience using Grails in almost ten applications. I can't compare against Ruby on Rails so I'll answer your other questions.
Has it overcome its buggy start?
- Yes it has. I've experienced a few Grails bugs on Grails 2.0.4/2.2.4.
Does it really confer rapid development benefits?
- It is pretty straight-forward to learn, easy to develop, never saw anyone with a good knowledge of the Java world take more than a work week to know the basics. Also easy to maintain. And you don't have to worry about your DB a lot - just make sure your're mak
Is the Eclipse plug-in better than it was and fit for purpose?
- Choose your IDE very carefully. Eclipse helped me a lot but it crashes and causes more trouble than it should. I went for IntelliJ and in the trial month it seemed a better choice. Lately I've been using Sublime Text, a few plugins and the old command line. I only go to a IDE in special situations - to use its debugger, for example.
Does it perform for real world production apps?
- It is kind of heavy. Research a lot on your design choices BEFORE writing your models. Do lots of research about good Grails design. Most of the things I've done two years ago I can realize how to make it better now since I'm more experienced. It handles real world production apps well but depending on the mistakes you make Hibernate can really be a headache.
