Tested and verified in both customer enviornment and in test enviornment.
In the event that you have a parent page restriction and a child page that inherits that restriction, upon upgrade, 2.9 will only respect the explicit parent permission in terms of security trims and actual access but not respect inherited child permissions. This only affects permissions that were in place prior to upgrade. New restrictions placed upon pages work fine.
When editing pages that are inheriting page restrictions, the page restrictions are shown to be in place, though the actual restrictions are not respected.