Regarding CEV: My own worry is that lots of parts of human value get washed out as "incoherent" - whatever X is, if it isn't a basic human biological drive, there are enough people out there that have different opinions on it to make CEV throw up its hands, declare it an "incoherent" desire, and proceed to leave it unsatisfied. As a result, CEV ends up saying that the best we can do is just make everyone a wirehead because pleasure is one of our few universal coherent desires while things like "self-determination" and "actual achievement in the real world" are a real mess to provide and barely make sense in the first place. Or something like that.

(Universal wireheading - with robots taking care of human bodies - at least serves as a lower bound on any proposed utopia; people, in general, really do want pleasure, even if they also want other things. See also "Reedspace's Lower Bound".)