[gutvol-d] translucent windows

the mac allows windows to have varying background opacity, from totally opaque through translucent to fully transparent... can anyone think of _any_ possible e-book use for transparent windows? because it looks really cool, and even though it's not cross-plat, i'd _love_ to be able to find _some_ reason to implement it... any reason. but alas, i'm coming up empty... ;+) -bowerbird