I've developed over 30 plugins using Grails 1.3.x and I got very strange exceptions related to GORM when I created my first Grails 2.0 plugin.
"No signature of method: grails.plugins.foo.Bar.save() is applicable for argument types: () values: "
Adding a service with 'static transactional = true' resulted in "No bean named 'transactionManager' is defined."
The solution was simple but I did not find it immediately.
grails create-plugin does not add the hibernate dependency in BuildConfig.groovy
grails create-app does
This must be documented so first-time plugin developers can avoid this kind of problems.
Both in the "what's new" section and in the plugin developers guide.