Well, it only makes the buttons/window titles in the taskbar opaque, not the whole area of the taskbar. So the space not occupied by window titles in the taskbar would still be transparent.
OS: Kubuntu 6.06 LTS (Dapper Drake) | KDE 3.5.3
Computer Specs: AMD Sempron 2200 1.5Ghz | VIA KM266 Pro 8235 chipset | nVidia GeForce MX 4000 128MB DDR-RAM 32-bit AGP 8x