the not-a-surprise-really-at-all Khan. He's perfect for the role, and an excellent villain. But, stripped of his history with Kirk, the battle between he and Kirk doesn't resonate as much in the shadow of Wrath. The death of Pike is sad, though almost inevitable in a way, I suppose. And that's good motivation for Kirk. But once that gets sidetracked and Khan and Kirk must team up (which I found very fun, btw) then they switch things around so that it's TWOK but Kirk and Spock reversed.
This is the least successful element of the movie, to me. Even some of the lines are the same. And it pulled me out of the movie. Some people were laughing a bit. It was just an un-needed thing, to me. I like this Kirk and Spock, but they aren't the original Kirk and Spock. This scene cannot hope to have the gravitas of the original, so why did they put themselves in this position? Especially when we could all figure the way out of it so easily?
The Vengeance is a cool nemesis for the crew. And the battle is pretty good, if short. It was great to see Nimoy again, though I found that scene to be a bit silly, too. "Hey, Old Spock - how do we get out of this jam? And can you explain why Khan is bad?" It felt like such a narrative short cut. And again, sort of pulled me out of the movie a bit.