I'd like to see stackable panels for KDE 4. That way I can put the "Run Command" applet and the system tray in the top one, and everything else in the bottom one. KDE 3.5 is so far the only DE that will do this for me (Xfce doesn't have stackable panels either, and GNOME doesn't have a panel applet like that.)
Here is the bug: https://bugs.kde.org/show_bug.cgi?id=165792
Please comment and vote!