Still waiting for the upgrade. Have to head out to rehearsal shortly so I'll probably get the upgrade when I get back.
If you want to upgrade, but retain the option of being able to roll back to the previous version in case of issues, go to applications in finder, right click on the Logic Pro.app and click on [Compress "Logic Pro.app"] to create a zip archive of your current version.
I've almost completely managed to wean myself off using third party plugins so I'm not worried about incompatibilites.