Quite a lot actually; the big news is eye control, as announced by Microsoft yesterday. This technology essentially lets you control Windows just by looking at it (it needs a third party piece of hardware, which then tracks your eyes and essentially turns them into the mouse). It's all very clever and very new, and at the moment quite restricted, but there's a lot of potential in this technology. Here's a quick video of gesture typing using eye movement.
The rest of this week's build is the usual collection of changes and enhancements to Edge (this week it gets a bit of a design make-over to make it more "modern" in appearance); plus some Windows Defender changes and updates, continuing it's rise to being 'actually useful'; oh, and full 24 bit colour support for the good old Windows console (otherwise known as Command Prompt / Powershell window (terminal to those Unix-y people here))