There's a huge amount of buzz kicking around right now about Microsoft's Silverlight, previously WPF/E. Broadly speaking, it is a challenger to the throne which Adobe Flash sits upon, but how realistic is that challenge? And what compelling developer and end-user features is Silverlight bringing to the fight?
Silverlight applications and controls are created using XAML, an XML-based language. Silverlight items are sent down the wire as plain-text, which Microsoft cites as an advantage over Flash; as plain-text, XAML will be indexable and searchable. This is "loose xaml", and Ted Patrick, Flex Technical Evangelist at Adobe, cites this as a disadvantage of Silverlight due to the inability to stream such files. However, one term floating around is XBAP, and I'm not sure exactly how this ties in with Silverlight - could these be used to overcome the problem that Ted mentions?
Version 1.1 of Silverlight will contain a version of the CLR which means that in addition to using XAML, you can work with Silverlight using C# and VB.NET; soon you'll be able to use languages such as Ruby and Python. This versatility is a boon, opening up the Silverlight platform to a huge variety of developers working with a range of development environments. Adobe provide two main methods of building Flash applications; the main Flash IDE and Flex.
Video is going to be a main area of competition between these two products. When youtube started using a Flash video player, video on the web became a lot less painful. No more clunky Windows Media or Quicktime plugins, instead the ubiquitous Flash player gave reliable streaming media to the masses. Now with their 1 megabyte Silverlight plugin, Microsoft have raised the stakes. By using the same codec which powers Windows Media Player, Silverlight could bring high-definition streaming video to the web in much the same way as Flash brought reliable standard video. This has been an issue for Flash for a while, so I suspect Adobe may move to fix this situation.
Of course all of this is neither here nor there at this time. Flash dominates the scene, with a market penetration in excess of 90% and if Microsoft want to make a dent they'll have to bring a lot of their cash and influence to bear. Maybe an Internet Explorer update could be on the way....?