Just got the new Titan X and did a cursory benchmark on a Matlab mex function.
It is not heavy on number crunching, so not representative of that case, but I was surprised to see it running at half the speed as the Titan Black with the previous driver.
So I ran the same benchmark with the Titan Black and the new driver, and it is half the speed from what it was before.
Obviously this points to a driver issue, rather than the hardware.
Could the latest (350.12) driver be that bad?