It's been a while since I've really worked with Grails. I used it in 2007 for about 7 months, but we really didn't use it in a typical fashion, as the front end was done in Adobe Flex. 2007 was also fairly early in the life of Grails; I remember using version 0.5.6 when I started at the client.
I'm now building a sample application in Grails 1.0.4 and doing all the AJAX stuff in jQuery. I'm really impressed with Grails now! It's so much more productive than I remember it. Also, I have a couple of books that have been absolutely essential to getting me going with Grails again: The Definitive Guide to Grails, Second Edition and Groovy and Grails Recipes. I'm using IntelliJ IDEA 8.1 for all my development and its Groovy and Grails support is much better than I remember it. JetBrains really makes it easy to give them money every year for a personal license upgrade for IntelliJ.
I haven't been super pleased with the Grails documentation on the Grails site and hopefully SpringSource has a positive effect on this issue in the near future. My development has been plowing ahead very nicely. I really like that I don't have to restart the application server for every little change. That saves a ton of time and has a positive effect on your ability to stay focused on job at hand. Very impressed with Grails this time around.