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To all the naysayers: This is incredibly progress compared to what I have ever seen with X. I can't make use of it (Mac user and I've no plans to switch), but I can appreciate it. And those saying that Longhorn will be able to do that forget that Longhorn won't be out for over a year and is backed by one of the largest companies in the world.
Also, the "just eyecandy" viewpoint is a flawed one, as any long-term use of Mac OS X will show. Smooth graphics rendering can really make a difference in users' perception of the speed of a computer.