I've used windows since 95. I've hated app data since vista. I've disabled UAC since that same time. I've spreaded the hate against the UAC since that same time.
As for the statistics, you should know that 87.342% of all statistics are made up on the spot.
Now, in all seriousness, I am not kidding, app data is evil! It should NEVER be purposely used! It was not meant for users to ever venture into, but instead as a (semi temporary) folder to hold program edited files which were in directories the user does not have access to (thus the reason it is hidden).