I'll keep it brief: there are some new props like Fence Panels which are supposed to act as walls but, in reality, have no collisions. For them to act as walls they need to be supplemented with "no-walk invisible barrier props". Can we please have those next update? Invisible barriers open up a lot of possibilities and freedom of design.
The one-skybox limit looks extremely odd.
Pre-set vanilla folders (let's take Battle Arena, for example) usually have two skyboxes to be used in tandem: one for background skybox and one for ground fog.
With the new cap the editor says only one of these may be used. That makes it impossible to bring our maps closer to vanilla standards.