Nik Cubrilovic has a great write up on Silverlight, Microsoft's latest technology to hit the street. A quick glance may leave one the impression this is a flash alternative, but that would be a false impression. Silverlight is a mini .Net CLR (runtime) that runs or launches from a browser. It supports Windows and Mac, IE, Firefox, and Safari, and can be written in C#, Javascript, Python or Ruby. Silverlight apps are written in XAML (aka .Net 3.0), so for developers it's not really a new framework, just a new method to run the app. Silverlight apps can also access the browser DOM meaning they can "talk" to the webpage they are hosted in and interact in ways we've not seen before.
While the "open source" camp will find reason to complain (there is just no pleasing them) I'm pretty excited about the technology. I've seen some XAML presentations and it's amazing what you can do with simple markup. The one I expect to make the most noise about Silverlight will be Adobe, having acquired Flash when the purchased Macromedia a few years back. Adobe has been itching for a fight with Microsoft, and it looks like they are going to get it.
It started simple, over file formats. Microsoft and Adobe went head to head on who had the "open" file format. (I added the quotes because the answer was neither.) The Microsoft became more open in Office 2007 and added an XPS format aimed directly at replacing PDF. It's hard to say who "won" that round - Microsoft released Office 2007 plugins for PDF (and OpenDocument), but that just means more reason for people to use Office 2007.
Now, the heat has been turned up on Adobe. Silverlight takes a hard swing at Flash, and if that's not bad enough Microsoft has lined up a suite of Expression Studio products aimed at designers. The advantage of Expression Studio is that it works hand-in-hand with Visual Studio - so developers and designers can work together on an application without worrying about one messing up the others work.
My advice for Adobe is to review what it is you do. You have not been a company supporting the development of applications, and if you try to fight Microsoft there your on their home turf. You have however been the artists tool of choice - use that to your advantage. Photoshop, After Effects, Premiere, etc - all of these are still the best tools in their areas. Don't let a fight over PDF and Flash (something you have only because you bought Macromedia) distract you from these other products.
In fact, once you realize Adobe you can live without controlling Flash and PDF, open source them. Get Flex, Flash, and PDF 100% open and you'll find a huge interest exists in these technologies. This is the biggest shot you can take at Microsoft and it will hurt. Timing is critical however, wait too long and you'll end up like Sun and Java - too little too late.