Exciting us about Blender 2.77 is that there are some CUDA GPU rendering improvements for its Cycles code. In particular, 3D textures for smoke/fire and point density are now supported. There is also optimized performance and memory use of subsurface scattering on the GPU to the point it's up to three times faster. There is also GK210 GPU support for the CUDA kernels and more.
Blender 2.77 is also bringing shader graph optimizations, increased limits of OpenCL textures, custom baking passes, modeling improvements, OpenVDB support, better threading, and many other changes.
You can read more about the changes for the upcoming Blender 2.77 release via the Blender.org Wiki.