I would be curious to find out how others view the platforms, especially from the standpoint of external application developers, but having been on the inside of both of these projects, here are some points of comparison. I’m attempting to be objective here and just point out some of the areas to consider. But since I used to work at Sun on Java/JavaFX and now work on the Flex team at Adobe you should filter appropriately.

-          Maturity: One of the reasons that you haven’t heard much about JavaFX to date is that it’s actually not yet released. Supposedly this will happen in the very near future, so maybe we’ll all hear more about it at that time.

-          Language: Although many of the underlying capabilities of JavaFX  rely on the Java SE platform, JavaFX itself is based on a new scripting language (not Java, not JavaScript, not ActionScript, but a new scripting language entirely). One notable differences between the languages of JavaFX and Flex is that Flex uses MXML for its declarative aspects, and ActionScript for the programmatic aspects. The JavaFX language combines both of these elements, having aspects of declarative and programmatic in the same code.

-          GUI capabilities: Both platforms offer GUI components, graphics, animation, and databinding capabilities, thought the platforms differ widely in syntax and capabilities of these different features.

-          Tooling: Most of the tooling so far announced for JavaFX are more on the code developer side; editing plugins for NetBeans, plus export plugins for Illustrator and Photoshop (they produce PNG files from the layers in the project). On the Flex side, there’s the FlexBuilder IDE and the in-development tools such as Flash Catalyst for designer/developer workflows and FXG roundtrip import/export from/to the CS tools including Catalys for the graphics tags in the Gumbo release of the SDK.

-          Runtime availability: The availability of the JavaFX runtime is basically that of the Java platform (if a user’s machine does not have the proper release of Java (I believe it will require the latest updated 10 release), they will need to download/install it). The availability of Flex is basically that of the Flash platform of the appropriate version (e.g., Gumbo will run on FlashPlayer 10).

Chet.