i thought it was a MS flash authoring tool when i first heard of it, but it's not flash at all.
liquidmotion revisited? it'll die just the same imo.
I think silverlight is WPF-E (Windows Presentation Framework Everywhere) based on the .net 3.0 WPF. so i'm thinking not a 'flash-killer' but a 'flex-competitor'. it sounds like it'll be for web-apps, not for animation. but we'll see.