I am usually not one to just repost the same information that others are posting on their blogs. However, I will make an exception in this case, because this information is THAT important. 93.3% of users in mature markets can currently view your Flex 2 or Flex 3 applications. That is huge. A year ago, I repeat just one year ago, this number was at something like 50%.
I am also no usually one to bash Microsoft and/or Silverlight, but I will be surprised if they get to 90% in the next 5 years.