Rather than start a new thread - as the OP already has an answer to their question, I'll post here.
This is a useful new feature of iOS 7 and I like how you can tweak it so updates only occur over WiFi.
There are two changes I would suggest for Auto App Updates, however.
Firstly, as it stands there is no indication of WiFi activity in the menu bar of the device when updates are in progress. Hopefully this will be added in the next beta.
Secondly and more importantly, although a useful feature, it's a bit of a battery hog. In addition to the WiFi only option I'd like to have the ability to select to update only when on WiFi and also connected to power.