Do you believe in an objective morality capable of being scientifically investigated (a la Sam Harris *or others*), or are you a moral nihilist/relativist? There seems to be some division on this point. I would have thought Less Wrong to be well in the former camp.
Edit: There seems to be some confusion - when I say "an objective morality capable of being scientifically investigated (a la Sam Harris *or others*)" - I do NOT mean something like a "one true, universal, metaphysical morality for all mind-designs" like the Socratic/Platonic Form of Good or any such nonsense. I just mean something in reality that's mind-independent - in the sense that it is hard-wired, e.g. by evolution, and thus independent/prior to any later knowledge or cognitive content - and thus can be investigated scientifically. It is a definite "is" from which we can make true "ought" statements relative to that "is". See drethelin's comment and my analysis of Clippy.
The latter question is the relevant one.
I have many problems with his book, but I think he is fundamentally taking the perfect approach: rejecting both intrincisist religious dogmatism and subjectivist moral relativism, and putting forward a third path- an objective morality discoverable by science. You're right though, he just presupposes "well-being" as the standard and doesn't really try to demonstrate that scientifically. Eliezer's Complexity of value sequence is the only place I've seen anyone begin to approach this properly (although I have some problems with him as well).
I see, but as I asked before what would satisfy as "an objective morality discoverable by science."? What would the world look like if objective morality existed vs if it did not? You need to know what you are looking for, or at least have a crude sketch of how objective morality would work.