Perhaps a better way to indicate iconified windows in the tasklist (instead
of enclosing it's title in `[]') is to just make the title "shaded" in a
similiar way in which the icon to the left is shaded.  To get an idea of
how it might look I created a mockup of this in The Gimp:
http://me.in-berlin.de/~lars/cruft/panel2.png.

Something like this would be better I think because it creates less visual
clutter and also makes it easier to see at a glance which windows are
currently iconified and which are not.

[ Btw.: What I first tried to do first was to use the same style for the
title of the iconified window as is also used in Gtk for insensitive
labels: http://me.in-berlin.de/~lars/cruft/panel1.png.  But this is bad I
guess because it gives the impression that the button would be disabled. ]

One possible problem I can see with my solution is that people using
screen-readers might not be able to tell the difference between iconified
windows and uninconified ones.  But I unfortunately don't know enough about
this topic to tell whether this really is the case or not.