I would like to enable mail notification.
I think it's a good for the product to update itself but at minimum I would like my customer to receive mail when it's done.
We can imagine everything is working and update is applied and something doesn't work anymore. If he has mail between, it will be easier to investigate and see an update was done between both different results.
I work only with "small" customer with less than 2K users and I think on these environment I can let update be done automatically but notification is necessary but it's not the default choice.