It has been observed that while the gray box painter (orange "S" logo) is being displayed, there is extremely high CPU consumption. This appears to be occurring due to a previous fix that went into 6u2; see Comments for details. This is severely impacting the startup time for JavaFX applets.
This shows up with the first launch of the basic Java / Swing version of BubbleMark from http://www.bubblemark.com/ .