I agree with the ars.technia summary of Mission Control:No, Snow Leopard is better. They're not at all the same. They had something great with Spaces, and then destroyed it all with Mission Control. Blech. Good thing they only charged 29 bucks, because anything more would be a crime.
The new behavior of full-screen windows and the surprisingly natural-feeling four-finger swipes used to switch between them and enter Mission Control means that many more Mac users will likely find themselves using these new features than ever used the combination of Exposé and Spaces in earlier versions of the OS.