Looking through the forum/and old JIDE release notes, I see some reference to the popup menu setDelay issue in java (and possibly JIDE tried to address this over a year ago).
Curently the JMenu.setDelay() is ignored by swing for hiding the sub-menus. After attempting to "fix" this issue myself and failing miserably, I looked into this further and some Java documentation claims that different L&F can have different implementation of usage of the setDelay() method.
I wanted to bring this to JIDE's attention (possibly resurrecting the issue) because it seems that this "bug" is low-proirity for Java, and even JDK7 (preview) doesnt seem to address it. Knowing that JIDE developers like a good challange and judging by the superior extensibility of the JIDE suite, implementing this in the JIDE L&Fs would be right up your alley.
In essence, this hiding delay is extemely important when multiple-level poup-menus are used. Any "wrong" movement in the mouse cursor causes sub-popup menus to be hidden immediately, which is a greate nuisance.
Let me know if i'm not being clear, and i can elaborate.