Dude, Flex kicks XAML's ass (or I want some of what Adam Churvis is smoking!)
. . . Adobe realizes its Flash-centric development model and tools cannot keep pace with Microsoft's XAML-based offerings. When you compare the two, Flash-based development looks like an unwieldy cobbled together tinkertoy. And there just isn't enough Adobe funding available to change that in any significant way, so they "give it up to the people" and let them join in for free.
What Adam states is probably completely true... in some alternate universe where rabbits have wings and amoebae are kings of the food chain!
Having seen XAML, I can only say that *it* looks like an unwieldily cobbled together tinker-toy -- a non-humanly-legible mess of low-level drawing primitives and high-level code with a styling/skinning system that exposes so much of the internals of the various objects as to be considered a gross violation of encapsulation. In other words, a trademark mess as only Microsoft (oh, bless!) can make one. Yuck! I can only think that XAML is such a mess on purpose so that you will be locked in to using the various Microsoft tools to create it. Tools, which I may add, pale in comparison to the excellent Eclipse-based Flex Builder. (The difference between the tools is like the difference between Windows and OS X -- the latter just works.)
Compare the unsightly accident that XAML is to the graceful high-level elegance of MXML and the difference is night and day. I could, if I wanted to, write MXML completely by hand without the aid of a development tool and compile it with a free compiler. I can't even dream of what a horrible experience writing XAML by hand would be without Microsoft's tools. More practically, I often switch back and forth between code view and design view in Flex Builder and that gives me complete control over my application. I can tweak the code as I need to while making use of the design view for rapidly creating and evolving the user interface. It's made possible by the fact that I can actually read and write MXML because it's an elegant, humanly-legible, high-level language.
If anything, Microsoft's tools currently have the leg up on how easy they make it to integrate with a back-end (at the cost, of course, of having that integration again lock you in to Microsoft technologies). This is the one area where we need better support in Flex Builder but in a technology-agnostic manner that works with multiple server-side technologies such as Java, PHP, Ruby, etc. (all of which now have open source Flash Remoting implementations).
Based on his comment, I can only assume that Adam hasn't used both XAML and MXML. Adam, try MXML and Flex and you can't help but see the difference. Until you do, please stop spreading FUD about Flex. Oh yeah, and there's no way Adobe is going to abandon Flex or anything else Flash-related. In fact, they're just getting started!