MXMLtips

Adobe released a Flex / AJAX Bridge. From Ely Greenfield's blog:

The Flex AJAX Bridge is a small, unobtrusive library of code that you can insert into a flex application, a flex component, a flash movie, or even an empty SWF file to expose it to scripting via the browser. Once you’ve inserted the bridge, pretty much anything you can do from Actionscript, you can do from Javascript.

A lot of what you can do in Flex is becoming possible in JavaScript, but that doesn't mean JavaScript is a better way to do it.

One reason is that the user experience with Flash is more consistent across browsers. AJAX behaves differently on different browsers - your app may work, but exactly how it behaves is somewhat browser-defined. With Flex, any browser that can host the Flash player (which is pretty much all of them, btw) will host your application exactly the same as every other.

Not only does this mean a consistent user experience, but it means you don't have to test your application with every browser known to man. How many times have you seen a shiny new AJAX application that "doesn't work on Firefox but we're working on it"? Or doesn't work on Opera, or doesn't work on Safari, or Camino, or ... The only disclaimer you're likely to have to use with your Flex app is that it doesn't work on Lynx.