Does a Magic Mouse let me use all the multitouch features of Lion? Does the magic mouse support all of the gestures that the magic trackpad supports, including but not limited to Launchpad and Mission Control?
NO
The Magic Mouse can open Mission Control with a double tap on the mouse's surface, but it does not provide a gesture to open Launchpad, a Lion only feature. However Launchpad can be launched with a Magic Trackpad with a four finger pinch.