What boggles my mind is when obvious usability problems persist over multiple versions of an application. (A quick example: Apple's spreadsheet app Numbers has

What boggles my mind is when obvious usability problems persist over multiple versions of an application. (A quick example: Apple's spreadsheet app Numbers has a behavior where the handle for moving a chart around on the workspace disappears if the chart is moved all the way to the left. It kind of docks the window, requiring an annoying work around to free it. There's no way anyone who uses it would not encounter this, but it's been that way for many years) The problem space of user facing features is overall quite complex. A developer can neither understand the beginning user's experience, nor the heavy user (they usually don't have the time to use their own application as a worker would, IDEs being an exception.) Just blindly adding features because a user requested isn't a solution for obvious reasons. I think a combination of user feedback, usability testing, quantitative analysis, along with creative problem solving by developers and product people is needed. Not to mention the nitpicky reality of there being an actual business case need for the feature.