: Fair warning, but I hate the trope above with the undying passion of ten
: million things that hate a lot. Mostly because of its use and abuse in
: Code Geass.
: "Oh, hey, we have this prototype mech that we hauled to the battlefield
: even though we don't have a pilot for it, and for no adequately explored
: reason it will only work with an exact match for a pilot... fortunately,
: we found this teenage reservist in the infirmary. Ran him through the
: simulator, and he's a 99.995% match, so we're going to drop him in the
: pilot seat and send him back out. Because $%#* training and common sense!
: Now call up his high school and make sure they have a place to stow it,
: because he's going to be the bodyguard for some British royalty that is
: attending the same school."

I agree, on the matter of training; if we're trying to be 'realistic' (whatever that means in sci-fi at least :P). See your timely space magic embed.

: Would a mech be easier to control just because it's humanoid? I dunno. You
: can teach someone to drive a car in a few hours, but true driving skills
: aren't honed until at least a hundred hours are spent behind the wheel.
: Mechs may be more 'familiar' at the outset, but how much practice would it
: take to get used to a higher center of balance, larger frame, and possibly
: a different range of mobility? And how much discipline would transfer over
: from driving vehicles to piloting mechs?
: Also: Don't pick your nose.

You keep saying higher center of balance. If the context here is a humanoid mech that's let's say ideally proportioned, then other than physically being farther from the ground, the center of balance is still proportional to body size. In essence, 'center of balance' isn't the issue as it's already relative to the body; it's having to adjust to the size of the machine you're maneuvering. But anyway, who says center of balance is inherently a positive or negative, IF engineering made sure the center of balance was in an optimal location for the mech already? CoB shouldn't be a problem in a good design.

: I wouldn't expect it, no.
: Humans are a tool using species. We easily grasp the idea of manipulating a
: stick to pick ants out of a log, or pushing an analog stick to make a
: character on a TV screen move in the direction we want.
: Wait. Are you talking about controlling a vehicle with a haptic feedback
: device, like some mechs are controlled?
: *shrugs*

Maybe. Who knows. Just another of your 'space magic' attributes, here for controlling the vehicle.

I should say, when arguing feasibility of a fictional machine class which is only usable through space magic, it's just as unfair to say "it is not possible" because.. you're saying the space magic isn't possible. Which..is kind of a pointless argument. Space magic is space magic because it recognizes that to the best of our current knowledge and scientific discoveries, some property is (/ies are) not possible. That's why it's magic.
And that's why I have issue with you saying mechs cannot ever be better than vehicles.

Mechs are another type of vehicle. They are an ideal vehicle designed to take advantage of human physiology on a necessarily larger framework - whether 1-2x a human size, or a hundred fold. Your "space magic" takes care of the how. What you're arguing is how believable you think any particular space magic is - whether based heavily on current science (more believable, but still not possible now), or heavily in fantasy and imagination (wow and cool factor, definitely not possible now).

: How far can you push fictional tech until it's functionally magic?

Fictional tech is magic. :P How magic seems to be the question. Some people like more magic, some people have a lower threshold for suspending disbelief. It's the stuff of nerd debates. Like debating the physics of Superman flying.

: Again, you seem to be approaching the problem from the vantage point of
: "What can I do to make a mech fit a role," instead of "What
: machine has the best qualities for the role that needs to be filled?"

Have you already created a selection of mechs from which to choose for specific roles? Because that's highly unfair and short-sighted. I'm saying why limit the possibility of what an engineer can come up with in a science-fiction environment? As they design a mech, and find shortfalls for a given task, they can either alter the intended task, fix the problem, work around the problem, or ignore the problem (bad! but possible; hide the weakness, hope the enemy never discovers it?).
Like I said, practically it's a non-answer. But it's also not short-sighted (for a fictional, future, mechanical construct)

: I'm just stating that legs are a structural weakness with no significant
: benefits.
: -That's not true. Legs must have some benefits that outweigh their drawbacks.
: What are they?
: -I don't know, but I'm sure they exist.
: What are they?
: -I don't know, but I'm sure they exist.
: What are they?

See above.
Also, a weakness in what context? Legs aren't just "a weakness". A weakness in doing what task? Compared to what? Once you provide that context, an engineer can address that weakness. Either vehicle B (mech or not) is better suited for the task than A or not. If not, should B be better suited than A? If so, how do we deal with said weakness? Fix it? Remove it? Work around it? If not, then A will be better for the task than B. But that's fine. Because B isn't intended to be better than A.
That goes for any vehicular tool, mech or not.

: Two thoughts: Notice that there's no axle or wheel in nature? No macroscopic
: organism moves along on wheels. There is no sort of shaft that can spin
: freely of a body. The closest thing nature has to using a wheel for
: transportation is the dung beetle. And, honestly, it sort of makes sense.
: Is it possible to have a contiguous circulatory system or nervous system
: between an axle and a body?

http://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems
Also, our blood cells are all detached from each other, swimming about and interacting with the physics of our body. Detachment isn't an issue. Each cell in the body has a task to carry out independent of all others, for which it's specially attuned (even if some others have identical tasks). Cells are highly complex structures. So the question of why wheels themselves aren't seen in nature I don't think is one of complexity or being structurally detached. *shrug*

: What is present in nature works for nature. Machines can take advantage of
: components that nature can't reproduce, like the wheel or the bearing. So,
: maybe the fact that the human form works for us doesn't mean that it works
: as well as other forms that are available to machines.

You've just explained a context in which wheels are more beneficial, and in which wheels are not beneficial. So I rest my case. (of course you'll point out that mechs are mechanical, and thus wheel should always been more beneficial?) pssh! Biological or mechanical, in the context of a tool, it's just another property. So, SPACE MAGIC; could it be possible that there's a machine for which legs can be beneficial towards a certain task or type of task? Of course! I dare you to say no. I dare you. Cuz then I'd just say Ok, we disagree. You can't disprove space magic :P

: My other thought is... intellectual? As in, mechs somehow taking advantage of
: our mental capacity in a way that vehicles can't? Color me skeptical.

What colour is skepticism?

: Oh, I blame 343i's writers for much more than the Mantis.
: In fact, since Kojima seems to be where they got the idea, maybe he deserves
: some blame too.

I'm not against having Kojima mechs removed from the Haloverse :P I'm not a mechspert or mechthusiast (I did it too), I just like to keep an open mind on the matter :)

: Maybe multipedes will fare better, but the average biped is burdened with a
: high center of gravity and low footprint. The bigger they are...

Relative to the ground.
But humans have a higher center of gravity compared to an ant relative to the ground. And we're both more capable than the other for certain tasks.
The ant can crawl up your leg, cause you to stumble into traffic and die, while it zips away unharmed.
But you can stomp on an ant.

: Anthropocentric bunk, most of it. When an android is involved, you just
: /know/ the conversation is going to go downhill fast.

meh, hey you're free to have an opinion. :)

: Jack of all trades, master of none, and always better than the master of one.
: Unless the fiction is emphasizing how warlike and insane we are compared to
: the rest of galactic civilization, in which case we are amazingly
: effective specialists.

Indeed.
Another reason why I'm intrigued by Captain Worf's possible spinoff ST series. A sci-fi centered on a non-human protagonist? ..Unless they focus on his desire to be more human, or fit in with humans, or whatever + humans, rather than just being himself, being a Klingon.

: Anything can 'work', provided that the design goal is narrow enough and you
: find enough rich idiots to buy it. Does it have a place in a hostile
: environment, where it may be shot at and people's lives may depend on it?

The term is "specialized". It's narrow, but it's specific and it's advantageous. Neither vehicles nor mechs have to have narrow uses. But perhaps that's a strength of mech styles - less versatile, but more potential in specialized tasks, if engineered competently. Hostile environment? Well, find a mech engineer (heck find them all) and see if they can come up with a mech design that is optimized for that specific environment, and performing a set of tasks in it.
Of course it's possible. "In theory" (best non-answer ever)

: I find that a good dose of vodka usually gets me out of your situation.

A good dose of vodka can usually get you out of any situation (by perception at least).