I looked into spray cooling solutions a couple years ago. I first read about it being used in the Cray SV2 (not produced). They were jet spraying flourinert againts the die and were able to double the amount of processors per cabinet than compared to air cooling. It speeds up the fluid cycle thereby reducing the amount of coolant needed (the main reason cray used it(flourinert=expensive)). If you could find a dialectric material that has similar properties to freon, you would be able to perform direct phase change in the same manner as direct die water cooling. The system stores less watts of energy, but can remove it at a faster pace. The drawback is, a failure in the system would be even more catastrophic due to less heat storage. An advantage is that the coolent is sprayed on with a high enough force that there is no thermal boundry layer adhearing to the surface to be cooled via surface tension.