Not "anything goes, do what you will", so much as "all X go, X is such that we want X before we do it, we value doing X while we are doing it, and we retrospectively approve of X after doing it".
As with a number of previous responses, that is ambiguous between the individual and the collective. If I could get some utility by killing you, then should I kill you? If the "we" above is interpreted individually, I should: if it is interpreted collectively, I shouldn't.
Yes, that is generally considered the core open problem of ethics, once you get past things like "how do we define value" and blah blah blah like that. How do I weigh one person's utility against another person's? Unless it's been solved and nobody told me, that's a Big Question.
There seems to be a widespread impression that the metaethics sequence was not very successful as an explanation of Eliezer Yudkowsky's views. It even says so on the wiki. And frankly, I'm puzzled by this... hence the "apparently" in this post's title. When I read the metaethics sequence, it seemed to make perfect sense to me. I can think of a couple things that may have made me different from the average OB/LW reader in this regard: