I've always used it, at least until "upgrading" to Windows 8 from XP.
For quickly viewing the contents of adjacent folders. Pressing an
arrow key is easier than pointing and clicking, especially for many
adjacent folders. I knew it was coming. I just don't understand the
reason Microsoft stopped including it, and it's annoying. What's the
point in just highlighting a folder name using an arrow key? What's
the point of leaving it out after windows XP? Looks like some
management decision by somebody who doesn't use a personal computer.