Role reversal didn't bother me so much, neither actor phone it in and no one went over the top. I actually laughed at the KHAAAAAAN from Spock though. If I want the original I'll watch the original, and probably will since this movie was really freaking forgetable.
1:The movie suffered from a hell of a lot of setup. WoK didn't need as much because the villian was already established. 2 was better than Darkness because it actually had some larger themes (Aging, the past coming back to haunt you) which this movie didn't have time to establish. If anything the theme of this movie was Kirk maturing and having to admit defeat, and the development of the Kirk/Spock bromance.
1a: The affore mentioned setup is what spoiled the last half of the movie. The moment Bones goes Dr. Frankenstein on the tribble all the trekkies knew the rest of the movie. Hell, I'm pretty sure Kirk's 'death' scene was word for word from ST2.
2: How the hell do you build a gigantic fucking Starship in secret? That whole thread about Admr. Marcus being a warhawk was stupid at worst, or a plot thread that wasn't fully developed. It would have been nice after having Section fucking 31 mentioned to have some cloak and dagger shit going on. Carol Marcus going from a Molecular Biologist to weapons specialist was unnecessary, at this point in the timeline she could be a generic science officer. But going back to my original point: Building a gigantic, overpowered weapon of destruction isn't going to go unnoticed. Someone above an admiral had to sign off on that.
3: The enterprise fell from the moon in less than 10 minutes. Hell, it felt like it was less than 5. FROM THE FUCKING MOON. Yeah yeah, furby powered deflector shields yadda yadda. It bugged me given that the only thing that should have been propelling it was the inertia from the torpedo explosions, which at that distance in outerspace wouldn't have been all that much on something the size of the Enterprise. But no, it falls like a stone straight at Earth after losing power in Lunar orbit. DERP. Also, it wouldn't have survived reentry falling into the atmosphere in an uncontrolled decent. I know, suspension of reality and the like. I just couldn't do it.
4: Killerprise flying out of the sky into San Francisco was awesome. More movies need skyscrapers being mowed down by airplanes/spaceships.
5: If Khan could teleport to Kronos, why couldn't someone else? If the area is known to be abandoned, a small special ops team would have been better than a starship that could cause an intergalatic conflict if discovered in the wrong area. I mean, if you really wanted Khan dead and he has no way to hide (see how easily Kirk found him), and you can teleport anything to the location, send in a team to mark his location then teleport the Torpedo's to where they can kill him remotely. We have drones in 2013, do they forget about them in the future?