I would like to use certain plugin in development environment, but would like to exclude this plugin from production and from generated war. What is the easiest way to accomplish this?
Yes, using plugin scopes. From http://grails.org/1.1+Release+Notes:
Plugins can now be scoped using either the environment or predefined build scopes:
def environments = ['dev', 'test']
def scopes = [excludes:'war']
The plugins will only load in those environments and will not be packaged into the WAR file. This allows "development-only" plugins to not be packaged for production use.