If I haven't experienced the translucent effect on iOS 7 I would be as skeptical as you are. But despite all the amateurish things Apple did with iOS (Oh the icons),the translucency is actually very tasteful and providing a satisfactory sense of depth.

The translucency on Vista is just over the top besides a heavy system resource toll.

I'll have to wait to see how the see-through side panel works in reality to give thumbs up to Yosemite though.