I see that we have Hubs, but Hubs don't always work the way we'd like them to. For example, say we have a Music+Video corner it would be much quicker to swipe the lock screen over and unlock and have a full screen of albums, artists and/or apps, personalized for each individual, associated with such. The Music+Video Hub does a pretty good job for most, but I feel like I'm taking unneeded steps sometimes. For instance, let say I wanted to open an app like fandango yeah it's in the Music and Video hub app section, but so is bloomberg, cnn, and the weather channel and other apps I don't primarily use for Video. not to mention, why would I open an app to open app.
As for folders, I would definitely welcome folders with open arms as well. The corners idea is just another approach.