I was having a quick look at the sample applications available @ http://www.javafx.com
& gave the 'Swirling Squares' a try.
While on the surface it appears to work ok, I don't think it's a good idea to be showing off Java2D's new(ish) translucent Frame support in a sample app. intended to demo. JavaFX capabilities.
Case in point, if you launch multiple instances of 'Swirling Squares' on a Windows XP machine, you will see system performance is absolutely destroyed.
Just 4 instances of the app. is enough to bring my Quad core Q6600 + 8800gtx to it's knees! (the entire O.S. becomes slow & unresponsive!)
While this is clearly a flaw in the underlying Java2D pipeline for translucent Frame rendering, most people arn't going to be able to make this distinction.
I think it's important the 'Java[fx] is slow' bandwagon is not let loose again...