I was getting frustrated, as were others, about the Mac OSX default column width in column view.
Yes, you could handily double-click the column handle and it would expand that column to the width of the longest file name (you knew that one right?), but I often have to use long filenames.
So I recently decided to change the default column width, opened Terminal and steeled myself to having to hack some core setting with some command-line arcane incantations. After a search of a few seconds I came across this video from Jason Glaspey
Change default column widths in Finder (Mac OSX) from Jason Glaspey on Vimeo.
What I love about this control of the interface is that I could have discovered it by accident but it was also put there on purpose, by an interface designer who thought about (or paid attention to user testing about) the sorts of thing a user might want to modify globally. In addition, the change is shown in real time, across all windows, communicating very simply and elegantly, the results of the change to the user, immediately, without text or technical explanations.
That is what good design, and good user experience is about.