Running gnome-packagekit under kde4, one sees it's systray icon misrendered (wrong size mostly). Per http://bugs.kde.org/155381 I traced this down to gpk-update-icon drawing the wrong size (32x32 minimum). $ xwininfo -tree ... [click on Plasma now] 0xc0007d "PackageKit Update Applet": ("gpk-update-icon" "Gpk-update-icon") 32x32+0+0 +951+762 ... $ xprop -id 0xc0007d ... WM_NORMAL_HINTS program specified minimum size: 32 by 32 ... Needless to say, the standard kde systray size is smaller than 32x32.
gnome-packagekit just uses GtkStatusIcon to see an icon name - and then leaves it up to GTK and the tray to set the correct thing. It also seems to work fine in GNOME... We'll use the main bug to discuss, as this isn't a GPK bug.