After a few preview releases, Unreal Engine 4.15 has now been released. One of the game changer features of UE 4.15 is the ability to cook Blueprints to C++. This means you can use the high level logic of Blueprint for developing or prototyping, but have the results compiled to C++ for better performance. On the topic of performance, compile speeds have also been vastly improved, up to 50% Epic claim. Support for the upcoming Nintendo Switch was also added, in an experimental form.
Major new features include:
Compile times for programmers are drastically reduced - by as much as 50%! Reloading content while Unreal Editor is running, Reroute nodes in Materials, a new Blendspace Editor, new mathematics Blueprint nodes, and more contribute to an even more streamlined development process in this release.
For those looking to squeeze out every drop of performance, Cooking Blueprints to C++ native code is no longer an experimental feature, the Texture Streaming system has gotten an overhaul, and Alternate Frame Rendering with NVIDIA SLI gives a boost on high end systems.
The Cinematics and Animation pipelines continue to strengthen with Animation blending now possible in Sequencer, linking Animation Curves to bones for culling in LODs, and modifying curves in Animation Blueprints with the Modify Curve node. Level Sequences can now be embedded in Actor Blueprints, and early support for Level Sequence Components is available for early adopters.
Developing for Nintendo Switch is available as experimental as part of the platform improvements. GPS data is now accessible on iOS and Android using the new Location Services. Also on iOS, streaming audio and remote notifications are fully supported. Monoscopic Far Field Rendering is an option for mobile VR platforms, HDR display output is available in an experimental state, and the ability to use Playstation VR Aim Controllers is also added.
You can read the much more extensive release notes here.