Just got back from seeing it. It was entertaining - but it's fading from my memory fast. I really don't understand why they bothered making Cumberbatch Khan. He's such an underdeveloped villain in this that it really could have been anyone. Almost a carbon copy of Nero in many ways.
This seems to be a common problem with Trek movies. Almost all the villains suck.
I'm wondering how he comes across as a villain to a Trek novice. I can't watch it without knowing his whole history and feeling the weight behind his words because of that.
I do think Cumberbatch was underused. Rather than have that 9 minute prologue of volcano neutralizing they should have had 9 minutes of Cumberbatch, showing us scenes that made us sympathetic or otherwise. We saw a lot of Khan in Space Seed before there was direct conflict, Khan with his people and interacting with Marla etc.. as a charismatic and mysterious individual. With ST:XII we miss all this, we see him in direct conflict the entire time other than a single exchange with the father. I think he really needed some build up and Cumberbatch being of the caliber he is it's a shame he didn't get it.