http://forums.sun.com/thread.jspa?threadID=5370797
the slowdown when using HTML in a list cell renderer with a huge
list model is all of the time spent calculating the preferred size for
each individual list item. That explains why the slowdown is only seen
on the initial display (or addition/removal of items), not while
scrolling. I think (it's been awhile since I looked at this) you
can work around it by calling setFixedCellWidth() and
setFixedCellHeight() in the JList (as doing both causes the JList to
skip calculating preferred sizes of all individual items). I know you
can work around it somehow, because I've done it before.