Hiding navigation elements – is this a good idea?

I was recently surprised by inadvertlently pressing the Alt key when viewing Vista’s Windows Explorer window (the file manager). The menu toolbar appeared as if by magic.

I commonly change the layout of my Vista and Windows 7 machines’ Windows Explorer to always show the menu. It has useful features not found elsewhere.  You do this by clicking on the Organize dropdown list and clicking Layout > Menu Bar. This is a persistent change to UI.

I was unaware that I could access it by pressing Alt. I found that the Alt key action also exists in Internet Explorer 7 and 8.

Is this a good or bad thing? If you know that using the Alt key reveals the menu it is a good thing. But if you don’t, and most of you didn’t before reading this, it is a very, very bad thing. Shouldn’t navigation elements be apparent, not hidden? We want to use our computers not search for hidden treasure.