I'd heard about it. I'd visited some Microsoft websites that talked about it. It always just sounded like another Flash. But this article over on arstechnica and the discussion around it (both there and elsewhere) turned a light on in my head such that I can at least see how this might be interesting for a whole lot of folks (though maybe not all). From the post:
Let me avoid the hype and get down to the real meat of what Sparkle is. Sparkle is a vector-based UI designer that supports both 2D and 3D objects. There are many applications for Sparkle ranging from Flash-like presentations to designing UI for windows applications.
I love it when people avoid the hype. Too bad so much of the discussion on arstechnica focuses on the hyper-headline.