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I was impressed by how quickly and easily my test application came together. I appreciated being able to run the end product (a .swf file) directly in a browser (with the latest Flash plugin) without even needing to deploy it to a server. I came away with the impression that, once you get used to MXML and ActionScript you could do a lot in a short amount of time. It's nice that, in general, the application looks pretty decent even if you're not a graphic artist. There tends to be at lot of focus on getting, displaying, and working with data from a server, particularly XML data, which is very useful. A primary drawback is the requirement for the client to have the latest Flash player.
Open Laszlo
Overview
Open Laszlo is a framework for building rich internet applications which can be deployed either to Adobe's Flash player or as DHTML in the browser.
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In comparison with Flex, an obvious benefit is the ability to use DHTML rather than Flash. It took twice as long and significantly more code to create essentially the same application with Laszlo as with Flex. The documentation for Laszlo is not as comprehensive as what is available for Flex.
Google Web Toolkit (GWT)
Overview
The Google Web Toolkit is a development toolkit for creating AJAX-based web UIs which are written in Java and compiled to javascript for deployment.
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