Possibly the most important feature of upcoming graphics APIs, albeit the least interesting for enthusiasts, is how much easier driver development will become. So many decisions and tasks that once laid on the shoulders of AMD, Intel, NVIDIA, and the rest will now be given to game developers or made obsolete. Of course, you might think that game developers would oppose this burden, but (from what I understand) it is a weight they already bear, just when dealing with the symptoms instead of the root problem.
This also helps other hardware vendors become competitive. Imagination Technologies is definitely not new to the field. Their graphics powers the PlayStation Vita, many earlier Intel graphics processors, and the last couple of iPhones. Despite how abrupt the API came about, they have a proof of concept driver that was present at GDC. The unfinished driver was running an OpenGL ES 3.0 demo that was converted to the Vulkan API.
A screenshot of the CPU usage was also provided, which is admittedly heavily cropped and hard to read. The one on the left claims 1.2% CPU load, with a fairly flat curve, while the one on the right claims 5% and seems to waggle more. Granted, the wobble could be partially explained by differences in the time they chose to profile.
According to Tom's Hardware, source code will be released “in the near future”.