There has been quite a bit of discussion in regards to whether or not Silverlight is a Flash killer etc.
I believe PiperJaffray Analysts said it best with this:
Microsoft’s Silverlight: Loud Bark, Soft Bite? KEY POINTS: • Microsoft recently unveiled Silverlight, a supposed Flash rival. • We expect Silverlight’s impact on Adobe’s business to be immaterial. • Flash is the web’s fastest growing video distribution platform on the web, and the developer community is committed to Flash as a standard for RIAs. • Adobe is pushing ahead in online video with Apollo and Adobe Media Player.
What Is Silverlight? Microsoft recently demonstrated its new Silverlight technology, a web development tool for rich Internet applications (RIAs) and a supposed rival to Adobe’s Flash and Flex. The Silverlight runtime is available as a cross-platform beta plug-in available for web browsers including Internet Explorer, Firefox, and Safari; Microsoft expects to have a final release by mid-2007.
Silverlight’s Impact Will Be Immaterial. We believe Silverlight’s impact on Flash and Flex will be minimal for three reasons: 1) Flash video technology is the fastest growing video distribution platform on the Internet; Adobe has a growing lead in the RIA space. YouTube, for example, which uses Flash technology, garnered an audience of ~45m unique users in March (up from ~13m a year ago); 2) Microsoft plays catch-up with Adobe, Adobe continues to innovate. On 4/15 we attended the NAB tradeshow where Adobe focused on its plans for online Video. Specifically, the company introduced Adobe Media Player, the next leg in Adobe’s video strategy, which builds on the success of Flash and implements the new Apollo technology; and 3) Web developers are loyal to Adobe (and ex-Macromedia) products, and now that CS3 integrates Adobe’s design products with the Macromedia tools, we expect the Flash developer base will become even more deeply entrenched in Flash and Flex as standards for RIAs. In early 2006, Adobe had announced that there were more than 2 million Flash developers.