One small change to the elevation interface in Windows 8 has to do with the image behind the elevation prompt. In earlier versions of Windows, the image was a snapshot of your desktop, including all your open windows. But in Windows 8, it's just a picture of your wallpaper. Why did this change?
We discovered that when you ran an elevated application, the screen capture performed by the elevation prompt often looked ugly because there was a good chance it caught an animation mid-stream. For example, when you run an application elevated from the Windows 8 Start page, the tiles zoom out, your name in the upper right corner fades out, and the entire screen cross-fades to the desktop. As a result, the snapshot showed your tiles in some intermediate location, a faint image of your name in the corner, and a half-visible desktop.
Okay, so work could've been done to, say, wait for all animations to complete before taking the screen capture. That and other solutions were proposed and considered, but the feature simply didn't make the cut. There were too many other things that had to be done, and those other things took higher priority.
Engineering is about trade-offs, and trade-offs are rarely easy. If you decide to do everything, then you find yourself trying to cram two years of work into one month of schedule, and that rarely ends well. You have to prioritize what is important and what is less important, and then exercise your creativity to come up with alternate solutions which, perhaps not ideal, get the job done in less time and with lower risk.