Matrixy scenarios have been discussed here and elsewhere (including xkcd and smbc) quite a bit, actually. Given that a superintelligence would be incomprehensible to mere mortals, it's kind of pointless to discuss this eventuality seriously. Plus you risk joining the dark world of anthropics. However, we can understand a similar situation from the other end: life of animals in the shadow of humans. Some of these humans are paperclip maximizers (displace animals to make room for crops), and others have an animal CEV value system (various animal rights groups). This has also been discussed a lot, of course. Unfortunately the only benefit of the latter discussion that I can see is that of a low inferential distance analogy in the fight to raise awareness of the potential dangers of "living in the shadow of superintelligence" to humans.
I observe that even animal rights groups are somewhat unlikely to assert the right of lions to eat humans, which an anthropomorphized lion would likely consider a fundamental value. So there's a limit to our Friendliness. :)
Although it regularly discusses the possibility of superintelligences with the power to transform the universe in the service of some value system - whether that value system is paperclip maximization or some elusive extrapolation of human values - it seems that Less Wrong has never systematically discussed the possibility that we are already within the domain of some superintelligence, and what that would imply. So how about it? What are the possibilities, what are the probabilities, and how should they affect our choices?