Is copper cookware really better than stainless steel? This is somewhat related to the question about copper vs. cast iron, but this is about copper vs. pure stainless steel.
I had an old stainless steel stockpot that warped (it was very, very cheap stainless steel, paper thin) and have to replace it ASAP.  I have a family member with a few connections that gets a deep discount on one of the more expensive brands.  I asked her to look into getting me a copper stockpot (lined with stainless steel, of course, so the reactivity problem more or less goes away), and got this response as an explanation to why it is apparently unavailable here:

[...] there is apparently no advantage cooking-wise to using copper, and people just buy it for the look.
[...] None of our big accounts, including [XYZ] etc even had any interest in stocking it, which is why we never brought it in.

Note that these stores do carry the same brand of stainless steel products, just not copper.
Now, I am taking this with a grain pile of salt because (a) this family member never cooks and (b) the advice came from a marketing manager who obviously wants to push the products that are available locally.  Nevertheless, I think it's worth asking people with knowledge/experience:
Is there actual evidence confirming any of the advantages of copper cookware (durability, conductivity, heat spread, etc.)?  Has it actually been proven anywhere that copper is (or is not) superior to stainless steel?
Or are articles like these just parroting a bunch of myths?
I'm looking for strong evidence here, so please answer only if you are prepared to back it up.
Clarification (with apologies to Ward): I am looking for evidence of the practical benefits.  It's obviously indisputable and easy to look up the fact that copper is a better conductor than steel, and lighter; the question is, does this matter with respect to responsiveness, hot spots, and so on?
Modern stainless steel pans with clad bottoms can be as good as copper pans.  McGee developed a simple technique to test the heat distribution where he fits a piece of paper to the bottom of the pan, placing the pan over a burner and carefully watching how the paper browns.  Thick aluminum, clad bottom stainless, and copper all worked equally well. 

There are differences that relate to the techniques used in cooking.  A thin copper pan is great for melting butter or chocolate straight on the burner.  Modern air-gap wall stainless steel pans hold the heat better and work better for simmering or boiling.  Copper is harder to upkeep.

Pans will develop hot spots, even copper which is the better conductor. Until we get graphite added to the cladding  or some other exotic material to distribute the heat, thickness will matter the most for even heat distribution.

I have read several consumer tests and reviews of pans and they fail to note that thermal conductivity and thickness can both be used in practice to balance the temperature distribution and heat flux in a pan.