He did definitely show what he was capable of in this version, jumping fantastic distances, cutting up Klingons like tracing paper, etc. That much of it I liked. What I didn't like was Cumberbatch's line delivery. His voice I was okay with, but he seemed to over-deliver the dialog with exaggerated wide-mouthed diction. Hard to describe, but I found it somewhat distracting, particularly in the brig interrogation scene.
Again, I still think Benicio del Toro would have made for a far better Khan. Not just because he, like Montalban, is of Hispanic origin and could lend a bit of exotic that the role should demand, but also because he can be just as menacing, but with an extra subtle hint of batshit crazy without going too over-the-top. Put some long hair on him with a ponytail, and HE is Khan incarnate, IMO.