It has been in preview since December, but Epic Games has finally released Unreal Engine 4.11 for developers to create awesome things with. This version focused on performance and the features that were added for Paragon, which entered early access two weeks ago. DirectX 12 is still considered experimental, and Vulkan is missing officially (although John Alcatraz has a tutorial to add it to Unreal Engine built from source), but the rendering back-end has received significant changes to accommodate the new graphics APIs in the future.
The three features that I'm most interested in, apart from free performance, are lighting channels, capsule shadows, and improved building of static light. Light channels are very difficult to implement in a deferred renderer, but Epic managed. This means that you can have dynamic lights only affect certain objects in the scene, either for performance, if enough lights are ignored to justify the cost of the channels themselves, or for special effects, like making a specific object stand out in a scene. They also added new shading models for eyes, hair, skin, and cloth, and added a bunch of interesting audio features.
Unreal Engine 4.11 is available now from Epic's Launcher. It's free to use, but Epic takes a royalty on certain revenues.