Grails update successfully from 2.3.11 to 2.4.4

I successfully update Grails from 2.3.11 to 2.4.4 by following https://grails.org/2.4.4+Release+Notes and http://grails.org/doc/latest/guide/upgradingFrom23.html. It was not a simple update due to a substancial existing web site.I had error at startup and many things to do to make it works.
So, here are some advices to help to complete this task :

Upgrade plugins

Be carefull, if you don't upgrade plugins like cache, hibernate, jquery, you will have stranges errors.

Plugin asset-pipeline replace resource plugin

You will have to move directory and organize them in assets directory and also change all include in GSP.Possibles surprises will perhaps appear : see http://stackoverflow.com/questions/27906139/grails-assets-directory-management

Plugin export:1.6

To now, it doesn't work for me

Templates

I delete templates directory end recreate it by command : grails install templates.
It fixes some errors.

Other 

There is a new annotation : @Validateable(nullable = true)