This is the second release to be officially labelled rs3_release, meaning it has come from the Creators Fall Update release branch of the Windows development tree. As such, there are no major new features as Microsoft start focussing on polishing the build for public release (due in about October).
Having said that, Microsoft has introduced a new font in this build called Bahnschrift. Here's what they have to say about it:
Our new first OpenType Variable Font Bahnschrift is now included in builds. This new font industry standard enables us to pack an entire typeface family into a single file with infinite variability. No longer are you constrained to simple weights like Light, Regular, and Bold. Now you can have an infinite range of font styles, with smooth interpolation from Light to Bold and beyond. Better still: because a single, efficient variable font can replace several static fonts, variable fonts save a lot of space. To learn more about variable font technology, see the articles in Wired, Designmodo, or Alphabettes.
Bahnschrift is our own rendition of the DIN font standard. Apart from being the standard road sign font in Germany and much of Europe, DIN is frequently used by graphic designers for its high legibility and clean, hard-working design style. Bahnschrift supports a smooth spectrum of weights from Light to Bold, as you can see in the above image. In this image, each letter is a slightly different weight than its neighbors. All these weights are “duplexed” – meaning they do not change in width when you change weight. You can switch from Light to Bold without changing the layout at all.
There's the usual skew of Edge updates, plus some new emoticons in this build. As usual, Microsoft's full release announcement is here.