Two words about this new Technology by Microsoft.
I saw it for the first time near the end of 2007, but I gave it no importance: yeah, cool graphics but, as I'm not a graphic designer and having so little taste in graphics :), I had no interest in learning the fundamentals.
Some weeks ago I came across the 1.1 alpha version of SilverLight, a complete version of the plugin, that can run on all main platforms (Win, MacOS, and a developing version for Linux) and on all main browsers (with only one plugin!!).
The main problem using FLASH with other technologies, such as .NET, is that you need a completely different environment to develop your applet (Flex) and have to use another language for your script (Action Script): moreover it's pretty difficult to generate both ASP.NET code and Flash code server-side, as they are in complete different domains. This can be done using third party solutions (such as SWFSource.NET, from this link) that allow you to generate SWF files server side, but at a too low level and of course without a complete intergration with the .NET technology.
At Microsoft Labs they wrote a scaled down version of the .NET platform to make Silverlight working: this allow you to write your client application in the same way you write your server pages, thus using the same data structures, objects and languages (C#, VB.NET, managed C++, ...), coming in help to the poor butcher programmer.
The framework, fully included in Visual Studio with few operations, comes with a completetly 2D rich model for drawing and responding to events (mouse click and this kind of stuff), some interesting streaming object for the mainly used video/audio standards (and Microsoft offers a 4Giga service of media storage and streaming server functionality in this link for free) fully customizable, a complete animation model and really interesting a full support for web services: this is what you will find in the 1.1 version, as the 1.0 is still something mostly related to graphical and animation manipolations.
No doubt that beeing an alpha release, I bet, there are still a lot of bugs and all the framework is missing some usefull objects not yet implemented, anyway this alpha is paving the way for a great new and useful technology.
Stay tuned for further readings, from your preferred butcher's shop!