I came across it for the first time a few days a go when the NBC olympics site required it for some viewing. no idea about it, though.

I downloaded and installed Silverlight Beta this week. My Windows and Microsoft updates are much faster, but otherwise I have noticed no difference since the installation.

Pam

it is just basically Microsofts product as a competitor to Adobe's Flash. Since it is a framework for providing rich applications to the Internet browsers.
"Windows users probably won't care whether the rich Web app they are visiting is using Silverlight or Flash. Both technologies require a small plug-in (as of IE7, Flash is no longer bundled with the browser) and once installed, both are invisible until the user hits a page that requires their services."

that is true if it works when we need it to then that is what most people care about. It will make more impact for publishers and web developers. Unfortunately they have not made it fully cross platform it is not for linux but there is an open source project in the works too called moonlight for linux.
This is a good article about silverlight and linux
Microsoft's Silverlight Promises to Disrupt Linux Web Users

here is the wiki on silverlight
Microsoft Silverlight