Yes, I saw it discussed previously, but none of the discussions involved a case in which the user has sucessfully installed CS PS5 Extended on the case-sensitive drive in question.

Thanks for your suggestion, but I did do my "homework" before posting.  I was hoping for an Adobe response that would be helpful.

No.  I'm not sure when I ended up with an Intel machine, but I certainly had the Intel version of CS5.

I understand that you're still working on it - that's great.  It does not explain why installation worked on this drive for CS5 and not for CS6.  It turns out that this boot drive is NOT case-sensitive; it is "Journaled HFS+" directly from the System Information panel (Serial ATA tab) from "About this Mac."

This means that while the idea of installing on a case-sensitive drive may have been "discussed to death," this presents a different problem that is unresolved.

Based on the error message that was thrown (I have no logs or anything else), I'm not sure I could have stated it more clearly.  Trying to install again, the specific error reads as follows:

[Red triangle with an exclamation point inside]  We've encountered the following issues

Installation on case-sensitive volumes is not supported.  Please chose a different volume for installation.

The only choice is "Quit" (that's the only button showing).

There's a second internal drive that is case-sensitive, but I'm not sure why that would matter.

Now I've solved this (no thanks to Adobe, in whom I'm very disappointed).

In the past, when you wanted to install something on your Mac, you'd simply copy a folder to your Applications directory.

As Photoshop (among other programs) has gotten more complicated, it's decided that it needs to install things in the various system directories and potentially in your user directory.

Herein lies the issue (and the solution, in this case).  My user directory is on the drive that is case-sensitive.  I don't know what Adobe needs to install there (since Photoshop is, after installation, available to all users), but that was the key.

SOLUTION:  Log in as another (administrator-enabled) user and install.  Bang - it works with no problems.

Yes, I still had to copy all of my plug-ins, etc. from PS5 by hand (and sort out the ones PS6 doesn't like - again by hand), but at least it's working.

Good software engineering practices dictate that installed software should PREFER case-sensitive drives, and not case-insensitive drives (think about the data). 

Good installation support (on the telephone) should at least suggest trying a different user account...

Adobe:  You owe me for my time on this one.  Where shall I send my bill?

...but not really out of the mainstream, right?

Software developers need case sensitivity (especially those who work in groups -- have you ever used "Subversion?").

Unix users need case sensitivity -- both developers and users (like me).

Web developers need case sensitivity (based on the servers they use).

There have been very long discussions about why case-sensitivity is "good" and "needed" (quick Google search will show you that), and, quite frankly, it's simply good software development practice.

We're just going to have to agree to disagree on that point.