Blender 2.78 has been a fairly anticipated release. First off, people who have purchased a Pascal-based graphics card will now be able to GPU-accelerate their renders in Cycles. Previously, it would outright fail, complaining that it didn't have a compatible CUDA kernel. At the same time, the Blender Foundation fixed a few performance issues, especially with Maxwell-based GM200 parts, such as the GeForce 980 Ti. Pre-release builds included these fixes for over a month, but 2.78 is the first build for the general public that supports it.
In terms of actual features, Blender 2.78 starts to expand the suite's feature set into the space that is currently occupied by Adobe Animate CC (Flash Professional). The Blender Foundation noticed that users were doing 2D animations using the Grease Pencil, so they have been evolving the tool in that direction. You can now simulate different types of strokes, parent these to objects, paint geometry along surfaces, and so forth. It also has onion skinning, to see how the current frame matches its neighbors, but I'm pretty sure that is not new to 2.78, though.
As you would expect, there are still many differences between these two applications. Blender does not output to Flash, and interactivity would need to be done through the Blender Game Engine. On the other hand, Blender allows the camera, itself, to be animated. In Animate CC, you would need to move, rotate, and scale objects around the stage by the amount of pixels on an individual basis. In Blender, you would just fly the camera around.
This leads in to what the Blender Foundation is planning for Blender 2.8x. This upcoming release focuses on common workflow issues. Asset management is one area, but Viewport Renderer is a particularly interesting one. Blender 2.78 increases the functionality that materials can exhibit in the viewport, but Blender 2.8x is working toward a full physically-based renderer, such as the one seen in Unreal Engine 4. While it cannot handle the complex lighting effects that their full renderer, Cycles, can, some animations don't require this. Restricting yourself to the types of effects seen in current video games could decrease your render time from seconds or minutes per frame to around real-time.