Flex is outrageously priced, and its future is in Flux now that Adobe is going to buy Macromedia.

Flex was inspired by Laszlo (in spite of the fact that Tim O'Reilly is confused and mistakenly thinks it's the other way around).

OpenLaszlo is an excellent open source web programming language based on XML and JavaScript. Your class declarations, object instantiations and configuration constraints are all defined in XML, with JavaScript expressions in attributes and JavaScript methods in text content.

OpenLaszlo strikes an elegant balance between XML and JavaScript, so Laszlo code is quite clean and easy to read and maintain. IBM has developed an Eclipse IDE plug-in for creating Laszlo applications with drag-and-drop and XML outline editors.

You can see for yourself how easy it is to develop interactive graphical web applications in XML+JavaScript with OpenLaszlo: Laszlo in 10 minutes. You can actually see, modify and run Laszlo scripts over the web, to learn how it works.

If you like Laszlo and want to learn more, then you can download the entire Laszlo source code, documentation and examples for free, and start developing your own Laszlo applications, without paying any exhorbinant licensing fees like Flex requires (on the order of $12,000 per server).