I've had fun playing around with JavaFx. I can't shake the feeling that it's in the same situation as Java was in 1996: targeted to a specific niche, but much more useful as a general-purpose language. Unfortunately, everything I've seen says that Sun (Oracle) intends to keep JavaFx in the RIA niche, a competitor to Flash and Silverlight.
And if that's their plan, here's my response: ain't gonna happen. Flash got to its position of ubiquity not so much because of technical merit, but because Adobe has mindshare among the graphical designers who are — like it or not — the arbiters of what goes on the web. At best, these people think of Java as “something to do with JSPs”; at worst, they think of applets (or more likely, negative folklore about applets, because they've never actually seen one). JavaFx is as likely to replace Flash as The Gimp is to replace Photoshop.
More important, Flash itself may not have much longer to run: there seems to be a strong backlash against plugins. Apple, with the iPhone and iPad, is the leading edge of this movement. However, the same attitude is showing up in desktop browsers, as you can see from the many pages describing how to make Java work with Chrome (I spent a half hour trying to get the latest Sun JRE to work with Chrome on Linux, but eventually gave up; call this statement sour grapes if you wish).
But, what about the mobile market? After all, the JavaFx tagline is “all the screens of your life,” and they've certainly made an effort to create one platform to span desktop and mobile applications. However, as you dig a bit deeper, you find that mobile device support is not quite ready for prime time: “Sun is working with Mobile Device Manufacturers and Mobile Operators to enable out of the box support for JavaFX.” What of the billions of Java-enabled handsets already out there? It appears that they're out of luck (although I haven't actually tried running a JavaFx app on, say, a Motorola RAZR). And, just in case you missed it, JavaFx will never find its way to the millions of iPhone users.
To wrap up: I believe JavaFx has a bleak future if it's confined to the RIA and/or mobile markets. But those aren't the only markets out there, and there's no reason that JavaFx has to remain confined. As I wrote when I started this blog, I like Java because it has a simple yet very powerful mental model, and the JavaFx language seems to have the same characteristics. It encourages a functional style of programming while still being object-oriented. There are, of course, other languages that do the same thing; Scala, for example. But those other languages don't have the Oracle marketing department behind them.
There's a lot of discussion about how Java is to evolve. But language evolution is a tricky thing. I could easily do without the mess that is auto-boxing; other people feel the same way about generics. And C has remained essentially unevolved since the 1970s, yet is still very useful (albeit in limited niches).
So I'll end with a question: will Java continue to acquire cruft, or is JavaFx the future?