Question... What happened with Interface Builder on Mac OS X? What made it not successful and why did it end up falling out of popularity? That was one of the features that was championed when Mac OS X was just starting and it was going to be the future of all GUI development on OS X. (Honestly GUIs have gone steadily downhill on OS X for quite some time as it's being overtaken by GUIs that look like they're designed for the iPhone.)