Win2k3, WB Beta2, NVIDIA GeForce4 MX 440 with AGP8X
I don't know if this is way it's supposed to work, or maybe it's a problem with my video card, but the taskbar isn't "really" transparent.
If I choose the aura or arrow skins I can see my wallpaper behind my taskbar. But if you move any windows behind the taskbar they aren't visible.
Other programs I use can make the taskbar truly transparent, so I can't imagine it does this on purpose.