The Amiga Workbench, had the ability to drag the full screen down by it's title and view the screen under it. This could be done multiple times. I haven't seen this done on any other GUI since, at least not to the best of my knowledge.
While the PC may not be the leaders of innovations with the UI, how does that matter to the average user? The best it could be for is bragging rights. Which of course don't pay back the corporate loans or create more marketshare.