It looks like this forum already has posed the "vs JavaME" and the vs Silverlight & Flash" questions. But how about Scala with its JVM and all that. It seems like Groovy and Scala were the next steps in terms of productivity and portability.
Scala and JavaFX share many concepts (they are both statically typed and feature support for functional programming) and even some similar syntax. They are both powerful languages, but while Scala is a powerful general purpose language JavaFX is meant specifically for graphically rich UI applications.
Using JavaFX and Scala together could be a very powerful combination, in my opinion.