Well, now I have.
The procedure is simpler than I was led to believe by the tutorial. Basically, the idea is (1) move ...\user\ to wherever you want it, and (2) set bootstrap.ini to reflect this. What could go wrong? Here's a detailed procedure that worked for me, together with some comments.
1. Close any open OpenOffice.org apps.
2. if enabled, disable Quickstart.exe. At Tools Options... OpenOffice.org Memory, uncheck "Load OpenOffice.org during system startup". This is just a safety measure to protect your customization in case you screw up in the steps below.
3. Copy ...\user\ to wherever you want it to be. For example:
copy: C:\Documents and Settings\<me>\Application Data\OpenOffice.org\3\user\
You can, of course, just move \user\ to the desired location. Copying is prudent.
4. In C:\Program Files\OpenOffice.org 3\program\bootstrap.ini, edit the UserInstallation= line. For example:
to be: UserInstallation=file:///D:/OpenOffice
5. Reboot the system. If Quickstart is disabled, you shouldn't get an error message here. Otherwise,If you get an error message about not finding a file, it's because you screwed up in step 3 or 4. Keep going. If you didn't leave a copy, move \user\ back to it's original location, and restore the UserInstallation= line in bootstrap.ini to it's previous value. Reboot the system to get back to where you started. You may or may not have lost your toolbar and keyboard customization, options, and so forth. Ah well. Painful, but not a disaster. Fix whatever went wrong in steps 3 and 4 and try again.
6. Start OpenOffice.org. The program should start in the normal manner. If the program begins by asking for your name, initials, and so forth, you have screwed up in steps 3 or 4. Don't continue. Cancel to back out of the dialog. Fix the problem and try again (steps 3, 4, 5).
7. Re-enable Quickstart, if desired.