I took the survey and answered every question. As usual, I found my ability to correctly answer the calibration questions comically bad . . . but hopefully well calibrated.

I completed every question on the survey that I could.

I took the survey and answered everything through the political compass.

I took the survey and was annoyed to realize that I didn't have a strong enough background to have informed answers to several questions.

If anyone knows of a really good summary for somebody who's actually studied physics on why MWI is so great (and sadly, Eliezer's posts here and on overcomingbias don't do it for me) I would greatly appreciate the pointer.

You say Eliezer's posts didn't do it for you, but how much of it did you read? In particular, the point about parsimony favoring MWI is explained in "Decoherence is Simple". As for the mechanism of world divergence, I think the answer is that "worlds" are not an ontologically basic element of the theory. Rather, the theory is about complex amplitude in configuration space, and then from our perspective embedded within the physics, the evolution of the wavefunction seems like "worlds" "splitting."

The first sentence lays out the issue:

"the law conservation of energy is based on observations within each world. All observations within each world are consistent with conservation of energy, therefore energy is conserved."

Conservation of energy takes place within worlds, not between them.

FWIW, I first learned about the MWI from: Paul C.W. Davies' book: "Other Worlds" - waay back in the 1980s. It was quite readable - and one of the better popular books on QM from that era. It succeeded in conveying the "Occam" advantage of the theory.

if multiple worlds really are "splitting"

What if instead of talking about "many worlds" we just said "no collapse"? If there's just this state and it evolves according to Schroedinger's equation. Then then of course there's conservation of energy.

For energy conservation see:

http://www.hedweb.com/manworld.htm#violate

The main reason for following the MWI is Occam's razor:

http://www.hedweb.com/manworld.htm#ockham%27s

I think that the many world hypothesis is aesthetic because it doesn't break symmetry. Suppose that in some set-up a particle can move down one path to the right or another path to the left and there are exactly equal probabilities of either path being taken. Choosing one of the paths -- by any mechanism -- seems arbitrary. It is more logical that both paths are taken. But the two possibilities can't interact: two different worlds.

In the world we experience, objects do occasionally move to the right. If there is not an alternate reality in which the object moved to the left, eventually, with either that object's movement, or the object that pushed it, or the object that pushed that, and so on, you have to explain how symmetry was ever broken in the first place.

Physicists don't like spontaneous breaking of symmetry. So much so, that the idea of many worlds suddenly seems totally reasonable.

Later edit: This is similar to the argument Eliezer made, in more detail and with more physics here.

On the issue of many-world, I must just be slow because I can't see how it is "obviously" correct. It certainly seems both self consistent and consistent with observation, but I don't see how this in particular puts it so far ahead of other ways of understanding QM as to be the default view. If anyone knows of a really good summary for somebody who's actually studied physics on why MWI is so great (and sadly, Eliezer's posts here and on overcomingbias don't do it for me) I would greatly appreciate the pointer.

In particular, two things that I have a hard time wrapping my head around are: -If multiple worlds really are "splitting" from our own how is this accomplished without serious violations of mass and energy conservation. (I'm sure somebody has treated this somewhere since it's so basic, but I've never seen it.) -Even assuming everything else is fine, the actual mechanism for which world diverge has to be spelled out. (Maybe it is somewhere, if so please help me end my ignorance.)

I'll admit that I haven't actually spent a great deal of time considering the issue, but I've never come across answers to basic questions of this sort.