We should start seeing more and better Apps. in the Store. Microsoft has announced they are changing how Developers are compensated for their Apps to get more Developers working on Win 10 Apps.
For those of you who are a big fan of Fluent Design (Acrylic) expect a lot more added in to the upcoming RS5 Builds. There is one new Acrylic feature though, which is transient UI. These mostly include pop-up menus, which will now have a layer of transparency. For those of you who were a big fan of Aero in Win 7, looks like it is coming back in upcoming RS5 Builds. Something Microsoft said would never happen. Bring back Aero. Remember the battle Cry "Aero IS DEAD" ?