To me it seems not wanting to plug in has very little to do with what we believe about happiness.<p>The most obvious reason of all to not plug in: That one actually cares about something in the external world. Sure, the machine could give the experience of parenting, but you know when choosing to plug in or not, that no child will actually exist in the real world as a result. If anything you experience in the machine will have no real world effects, then if you care at all about the real world, that should be reason enough not to plug in.<p>Perhaps he is considering a somewhat harder case where the world within the machine is "real" in the sense that anything you produce in the machine lives on in the machine. So if you have a child in the simulation, that child is not just in your simulation, but will live on after you are gone, just like a real child. Then the question becomes more: Do you trust that the simulated world is better than the real one? I wouldn't be an early adopter, but I'm sure some people would be willing to make that jump.
The "Suppose there was a" conversations get kind of annoying when they start to talk about things that are not likely to exist anytime in the near future, like a perfect virtual simulation of the world.
Sometimes when I am feeling punky while talking to a creationist, I will tell them that my belief is similar to theirs.....I believe we were all created ten minutes ago, with all our memories.