Thanks for the comments!
(a) the existing installation is not detected with a bailout option ("blah blah already installed blah blah do you want to continue?")
This should probably wait until there is a distutils registry of installed modules.
Is this in the works?
(c) you are prompted for EACH file as to whether to replace or not; there is no "yes to all" (or "no to all") so one would potentially have to click "yes" or "no" hundreds of times to complete for something like PyXML.
Seriously: I should add this. My excuse: The yes/no to all is asked once just before the start of the installation.
Yes, I retried my "operator error" intentionally later just to confirm, and this time I noticed that initial box. I /think/ the problem was at that point I didn't yet know I was in trouble.... it was already a while ago so I don't remember that clearly.