VI – last time i had my very personal fight with this text editor was back in 1992 or 1993 when sitting in a Oracle Administration trainging class, and probably was the only non-UNIX guy (some time months later I was the first Windows guy that installed Oracle on NT 3.51). Now nearly 15 years later again i come across that editor and NO i have not learned how to use it since then because so far my focus was on things where VI would not be needed, but my interest in Virtualization technologies seems to drive me somehow towards learning this VI editor , or at least the basics, like how to get out of that thing !. I had just edited a vmware configuration file on ESXi, but then found myself in not being able to save that file and exiting from VI.
The references below seemed to be helpfull.
http://www.unix-manuals.com/refs/vi-ref/vi-ref.htm
http://en.wikipedia.org/wiki/Vi