I surmise from your comments that you may not be aware that Eliezer's written quite a bit on this matter; http://wiki.lesswrong.com/wiki/Complexity_of_value is a good summary/index (http://lesswrong.com/lw/l3/thou_art_godshatter/ is one of my favorites). There's a lot of stuff in there that is relevant to your points.
However, you asked me what I think, so here it is...
The wording of your first post in this thread seems telling. You say that "Refusing to become orgasmium is a hedonistic utilitarian mistake, full stop."
Do you want to become orgasmium?
Perhaps you do. In that case, I direct the question to myself, and my answer is no: I don't want to become orgasmium.
That having been established, what could it mean to say that my judgment is a "mistake"? That seems to be a category error. One can't be mistaken in wanting something. One can be mistaken about wanting something ("I thought I wanted X, but upon reflection and consideration of my mental state, it turns out I actually don't want X"), or one can be mistaken about some property of the thing in question, which affects the preference ("I thought I wanted X, but then I found out more about X, and now I don't want X"); but if you're aware of all relevant facts about the way the world is, and you're not mistaken about what your own mental states are, and you still want something... labeling that a "mistake" seems simply meaningless.
On to your analogy:
If someone wants to "keep her body natural", then conditional on that even being a coherent desire[1], what's wrong with it? If it harms other people somehow, then that's a problem... otherwise, I see no issue. I don't think it makes this person "kind of dumb" unless you mean that she's actually got other values that are being harmed by this value, or is being irrational in some other ways; but values in and of themselves cannot be irrational.
[Eliezer] can't stand the idea that scientific discovery is only an instrument to increase happiness, so he makes it a terminal value just because he can.
This construal is incorrect. Say rather: Eliezer does not agree that scientific discovery is only an instrument to increase happiness. Eliezer isn't making scientific discovery a terminal value, it is a terminal value for him. Terminal values are given.
In this discussion we are, of course, ignoring external effects altogether.
Why are we doing that...? If it's only about happiness, then external effects should be irrelevant. You shouldn't need to ignore them; they shouldn't affect your point.
[1]Coherence matters: the difference between your hypothetical hippie and Eliezer the potential-scientific-discoverer is that the hippie, upon reflection, would realize (or so we would like to hope) that "natural" is not a very meaningful category, that her body is almost certainly already "not natural" in at least some important sense, and that "keeping her body natural" is just not a state of affairs that can be described in any consistent and intuitively correct way, much less one that can be implemented. That, if anything, is what makes her preference "dumb". There's no analogous failures of reasoning behind Eliezer's preference to actually discover things instead of just pretend-discovering, or my preference to not become orgasmium.
That having been established, what could it mean to say that my judgment is a "mistake"? That seems to be a category error. One can't be mistaken in wanting something.
I have never used the word "mistake" by itself. I did say that refusing to become orgasmium is a hedonistic utilitarian mistake, which is mathematically true, unless you disagree with me on the definition of "hedonistic utilitarian mistake" (= an action which demonstrably results in less hedonic utility than some other action) or of "orgasmium" (= a ...
(This is a semi-serious introduction to the metaethics sequence. You may find it useful, but don't take it too seriously.)
Meditate on this: A wizard has turned you into a whale. Is this awesome?
"Maybe? I guess it would be pretty cool to be a whale for a day. But only if I can turn back, and if I stay human inside and so on. Also, that's not a whale.
"Actually, a whale seems kind of specific, and I'd be suprised if that was the best thing the wizard can do. Can I have something else? Eternal happiness maybe?"
Meditate on this: A wizard has turned you into orgasmium, doomed to spend the rest of eternity experiencing pure happiness. Is this awesome?
...
"Kindof... That's pretty lame actually. On second thought I'd rather be the whale; at least that way I could explore the ocean for a while.
"Let's try again. Wizard: maximize awesomeness."
Meditate on this: A wizard has turned himself into a superintelligent god, and is squeezing as much awesomeness out of the universe as it could possibly support. This may include whales and starships and parties and jupiter brains and friendship, but only if they are awesome enough. Is this awesome?
...
"Well, yes, that is awesome."
What we just did there is called Applied Ethics. Applied ethics is about what is awesome and what is not. Parties with all your friends inside superintelligent starship-whales are awesome. ~666 children dying of hunger every hour is not.
(There is also normative ethics, which is about how to decide if something is awesome, and metaethics, which is about something or other that I can't quite figure out. I'll tell you right now that those terms are not on the exam.)
"Wait a minute!" you cry, "What is this awesomeness stuff? I thought ethics was about what is good and right."
I'm glad you asked. I think "awesomeness" is what we should be talking about when we talk about morality. Why do I think this?
"Awesome" is not a philosophical landmine. If someone encounters the word "right", all sorts of bad philosophy and connotations send them spinning off into the void. "Awesome", on the other hand, has no philosophical respectability, hence no philosophical baggage.
"Awesome" is vague enough to capture all your moral intuition by the well-known mechanisms behind fake utility functions, and meaningless enough that this is no problem. If you think "happiness" is the stuff, you might get confused and try to maximize actual happiness. If you think awesomeness is the stuff, it is much harder to screw it up.
If you do manage to actually implement "awesomeness" as a maximization criteria, the results will be actually good. That is, "awesome" already refers to the same things "good" is supposed to refer to.
"Awesome" does not refer to anything else. You think you can just redefine words, but you can't, and this causes all sorts of trouble for people who overload "happiness", "utility", etc.
You already know that you know how to compute "Awesomeness", and it doesn't feel like it has a mysterious essence that you need to study to discover. Instead it brings to mind concrete things like starship-whale math-parties and not-starving children, which is what we want anyways. You are already enabled to take joy in the merely awesome.
"Awesome" is implicitly consequentialist. "Is this awesome?" engages you to think of the value of a possible world, as opposed to "Is this right?" which engages to to think of virtues and rules. (Those things can be awesome sometimes, though.)
I find that the above is true about me, and is nearly all I need to know about morality. It handily inoculates against the usual confusions, and sets me in the right direction to make my life and the world more awesome. It may work for you too.
I would append the additional facts that if you wrote it out, the dynamic procedure to compute awesomeness would be hellishly complex, and that right now, it is only implicitly encoded in human brains, and no where else. Also, if the great procedure to compute awesomeness is not preserved, the future will not be awesome. Period.
Also, it's important to note that what you think of as awesome can be changed by considering things from different angles and being exposed to different arguments. That is, the procedure to compute awesomeness is dynamic and created already in motion.
If we still insist on being confused, or if we're just curious, or if we need to actually build a wizard to turn the universe into an awesome place (though we can leave that to the experts), then we can see the metaethics sequence for the full argument, details, and finer points. I think the best post (and the one to read if only one) is joy in the merely good.