There is a Notification Center listing that tells you "X amount of apps were updated". When swipe that notification over, it takes you to the App Center update panel which lists the apps that were updated and tells you the changes when you tap the down arrow, like normal.
That is excellent that it's optional! I like to read the notes, and there are some apps I hold off on as long as I possibly can before updating. I'm really happy to see this news. Thanks for the SS!