What exactly is this "Anniversary Update" anyway?
The first such sub-version release was 1511 (i.e. a build from 2015, November), and this Anniversary Update is version 1607 and happens to be one year after the release of Windows 10, which is why they called it "Anniversary Update".
If there's anything Microsoft is consistent about, it's inconsistency.
Well, unless you fancy digging around in the Registry, but yeah, they removed the GUI-toggle for it.
More seriously, though, the biggest thing is that they added Ubuntu-support with this update. The rest of the features are pretty boring.