Apple effectively deprecates the Quit command
Lion is far more than just new user interface features. Apple have fundamentally rethought the human computer interaction at a much deeper level. There are radical changes to the nearly thirty year old document model and quite fundamental changes to the human interaction with the process model.
Applications without processes. Processes without applications. Did Lion just blow your mind?
These are very impressive, significant shifts.
If you haven’t read the Ars Technica in depth review of Lion, and you are interested in the geeky underpinnings of the changes, you owe it to yourself to read all 19 pages. John Siracusa has again written the best review out there of a new OS X release.