David Tesar published an interesting guide on SIlverlight deployment:
This guide is intended for any organization who would like to deploy, manage, and troubleshoot Silverlight in their environment. Some of the things you can find in this guide are installation switches, update behavior, value proposition on why to deploy, group policy adm / admx / adml files, and instructions on how to deploy Silverlight via group policy & SMS.
Back in May of this year I was presented with a side project to work on by Tim Sneath for this guide. I accepted and it's great to have it finally released. I had help from our SMS team doing a test deployment to 60k machines using the document, documentation reviewed by a number of people, and of course help from the Silverlight product team.
As an FYI - Efforts were made to create an MSI of Silverlight which could be deployed via group policy in addition to the script method, but there were challenges with this based on the way Silverlight inherently installs. The Silverlight EXE extracts into an MSI and MSP file - both of which are required to install in order for Silverlight to function. So if we gave you this version of the MSI, you'd have to go back and install the MSP separately after the MSI install (yuck). In trying to package the exe into an MSI, you can't have two MSI files trying to install at the same time - so this doesn't work either.
At any rate, the guide still shows you how to install Silverlight via group policy using the provided script. Each group policy method (MSI and script) have advantages and disadvantages; the script method should be sufficient for most organizations. In the future, there will be more installation/upgrade options and updated versions of the guide. Future availability of a MSI package for group policy deployment is uknown at this time.
So please, download here and feel free to provide feedback.