As I am going through the "Definitive Guide to Grails", I can definitely say that for the most part things are going well. I wish that the dynamic update feature would work, but other than that things are going well.
One thing that has been hitting me like a pile of bricks, is Grails' use of injection to put properties and methods onto an object without it needing to extend a base class. This is all fine and dandy, but who can remember all those extensions easily for like a domain class? I know the IDE can.
As work has been progressing on method completion on the Groovy Eclipse plugin ( great work Ed ), it occured to me that adding additional completion options based on the fact that the project is a grails project should not be very hard, not hard at all. In fact, I did something similar in Groovy Monkey to add autocompletion and elements in the outline view based on what the script's binding was. How cool would that be, to not have to remember the domain's class' get, what actions are injected automatically into a controller, to perhaps provide some assistance to using the findBy* methods?
In fact, the way I think about it, using conventions is a bit like having static type information around. And if you have some equivalent of static type information, don't autocompletion and other IDE goodies follow?