- no Linux (or OpenSolaris ;-) support yet. Really a missed opportunity to get 'Java' in a more positive spotlight in the Linux users' mindset.
- native Mac and Windows video formats are supported, but to get real cross-platform media, FXM must be used (http://java.sun.com/javafx/faqs.jsp#19). Supporting native video formats but claiming full cross-platform support seems contradictive to me.
- I could still see some small glitches like small GC-pauses and startup-waits. Not sure if those are relevant or just demo-quirks.
- the promise of 'multiple devices, one language' is still very vague to me. I have no clue how full screen apps can run great on small phones without any change.
- licensing is still blurred. Although Sun is committed to opensource the Java FX core (http://openjfx.org). Real open source of Java FX would be a big plus compared to Flash, especially for the Linux distro's, but I doubt Sun will be able to remove all encumbered stuff like the multimedia codec's.
I'm not really a "shiny flashy apps" developer, but once Linux support is there I might delve deeper into Java FX.