I came accross this article that gave 10 reasons why Flash is better than Silverlight. I agree with some of the comments there that the article is biased and Microsft has got several good things built into Silverlight. However I think it is too early for someone to drop Flash and consider developing Silverlight  applications- especially when Silverlight is installed only on fraction of the computers than Flash. I don’t know how many Silverlight developers are out there, but I doubt if it is anywhere near number of Flash developers. Nevertheless, it is being promoted by Microsoft and should be followed closely.