Why would there be no underlying desktop? While you can have lots of desktops, their icon contents will be the same on each one. It would make complete sense for me to want to drag an image from Safari in full screen onto the desktop, but it's impossible because you can't show the desktop while in full screen.
The problems with full screen in Lion are:
- Can't show desktop
- Can't show dock with Wacom Tablet (because of absolute positionning)
- Quitting and reopening an app will always bring it out of full screen mode
- Full screen apps create more desktops, so if you already have loads, swiping from desktop 1 to desktop 5 is a huge pain with 3 full screen apps and 5 desktops in between
- Slow animation that brings the app in and out of full screen
- Activating Mission Control while in a full screen app will show Desktop 1 - why? I completely lose track of where the hell I am
- Putting something in full screen places it on the far right if you don't check "Automatically Rearrange Desktops"
so I never use Full Screen, I really hope ML addresses most of these...