Came across this very interesting and well argued article by Edward Clint from "Critical Thinking" that does a pretty good job trashing the Prime Directive (or at least the PD when it is absolute). It argues the PD is morally indifferent and blindly dogmatic, a rule upheld "by force and not reason." The consequences of not violating it are irrelevant. A person can let millions or billions die, and feel principled and self-satisfied for having done it.
More on topic, it won't ruin the movie for me, but it's distressing to see the TNG version of the PD (the strictest of all) in STID. What Kirk did on Nibiru was correct. There should be no punishment. What's he supposd to say, "I'm sorry I saved hundreds of millions of people from extinction. It won't happen again." I'd be more wary of the character of a Starfleet officer who could coldly turn his back on potentially millions of people only because they are too "primitive" to be saved. Too bad that volcano couldn't have held off until those folks invented warp drive.
It would've been neat (and make it even more morally ambiguous) if Nibiru was a 21st century Earth type of industrial culture with billions of people. Someone captures the Enterprise over the volcano on a video camera. It'd be all over their version of Youtube in hours. There are thousands of videos of UFOs out there, and while they may have created a cottage industry on the subject, they've hardly changed our cultures in any dramatic macro manner.