Usually I've received Xcode updates as regular updates from App Store, but this time around I'm seeing nothing (I've got 7.3 installed already). IIRC I think I've downloaded Xcode releases through the developer program before, but if this now has changed does it mean I need to install it as a regular App Store package to receive updates etc automatically from now on?

Weird stuff. On my laptop (which is about as identically set up as I've managed) the Xcode update arrived as expected automatically.