One thing that really bugs me about both the Windows 8 start screen and the Android app switcher is that they just haven't quite got the whole "overview" screen white right. Let me explain…
My point of reference is Gnome 3 where the super/windows key switches to the menu mode. The current apps all shrink down and rearrange themselves in an exposé style display, and you have the option to rearrange them, close apps down, or start new ones. You can click an app to focus on it.
Windows 8 Start Screen
In the Windows 8 desktop, the super key brings up the start screen. This flips up from nowhere and shows a list of "tiles" which are essentially just widgets and mostly represent apps you can launch. One of these tiles is the "desktop", which is basically just a big rectangle with your desktop wallpaper in it.
Coming from Gnome, this strikes me as weird, because the desktop is presented as "just another app". You can't interact with it, can't see what's actually running in it, and clicking the tile just takes you back where you were before you "start"ed. At present it serves almost no purpose, because you can get back to the desktop using the super key or swiping the bottom left corner, so I'm not entirely sure what the point of it is.
It's very strange and I think it could be vastly improved it it contained an actual snapshot of the desktop contents, or if it could be interacted with in any way.
Android App Switcher
The app switcher lets you switch between running apps, and it does this by showing a column of cropped screenshots of recently running programs. This is very similar to Gnome, except the metaphor is different: instead of "zooming out" to get an overview of running apps, the switcher just pops over the top of the current running interface.
The major drawback of doing this is that the currently running app isn't displayed on the switcher, because it's still running underneath the switcher. This means it's not immediately clear how to get back to the current app (hit the hardware back button) and it also causes the icons to all change positions in unexpected ways when you do switch apps more than once.
This could be improved vastly if the app switcher showed a "zoom out" animation, shrinking the current app down to a thumbnail and having the others appear to the top, as if they've been waiting just offscreen the whole time
In conclusionThese are both modern, square interfaces and in both of these cases it would make much more sense to me to have some kind of spatial affinity represented visually with a zoom animation. This would primarily allow the user to see what the interface is doing and give them an easily visible escape route if they decided they didn't want the menu after all. It also emphasises the overview aspect, and makes it clearer that this is where you go to get stuff done.
So there's my mildly ranty post. The overall theme I think I'd like to see is more zooming and less arbitrary animation, but maybe that's the Gnome fan talking.