The one quibble I have with your response list (which is good, don’t get me wrong) is that the skills in hacking a Unix or Unix-like system are necessary if one is going to get into s/w development on anything but a Windows system. eg, if you’re going to work on routers or security appliances, web servers, etc - you’ll likely be working on some manner of Unix system as either your development environment or the server.
The “back end” side of computing is very heavily controlled by Unix now. If a person is interested in writing s/w for the server/blade/embedded market, they’d better learn Unix.
Your point about differences between various flavors of “Unix” is very important. For those who aren’t Unix aficionados, they should know that there are two major camps in Unix-land: POSIX/Linux and BSD. They’re nowhere close in terms of file layout on the disk, or the programming API’s. When was a young noob on Unix, it was in the infancy of the AT&T SysV vs. BSD 4.2 wars, and the internecine warfare in Unix-land was just heating up.
After using or hacking on many flavors of Unix from Seventh Edition on PDP-11’s to OS X and Linux/*BSD, I can say that the beauty of Unix is that you can write one base of software.... and debug it everywhere after you re-compile and link it.