I've written 4 blog articles on the JavaFX sequence implementation that should be of interest to those who want to know how it works and what it costs.  This covers the 1.2 Marina implementation.

This is probably the best order to read them:
http://per.bothner.com/blog/2009/JavaFX-sequence-basics/
http://per.bothner.com/blog/2009/JavaFX-unboxed-sequences/
http://per.bothner.com/blog/2009/JavaFX-sequence-updating/
http://per.bothner.com/blog/2009/JavaFX-sequence-triggers/