Mission Control in Mac OS X Lion has a hidden motion blur effect that can be enabled quite easily:

Enter Mission Control as usual

Press Command+M to enable motion blur

to enable motion blur Re-activate Mission Control to see the effect in action

You can then see the blur effect by moving about with the standard Mission Control actions, from entering and exiting into Mission Control, clearing the desktop windows, switching between desktops, to selecting apps and windows.

It’s a nice effect, but the motion blur can get slightly choppy on older Macs or machines with less available RAM, which is probably why Apple didn’t ship the effect as enabled by default. You can always disable blur by pressing Command+M again.

Similarly, a blur effect can be enabled in Launchpad by using the same keyboard shortcut. Both of these bits of eye candy were seen in the original presentation for OS X Lion at the “Back to the Mac” event.

The Blur in Mission Control does not appear to exist in the oldest nor most modern versions of Mac OS X so this is limited to the mid releases (for now anyway).