Exactly. Also, it doesn't seem to have anything to do with Core Image.We know that it can do the "translucency" effect (transparancy + blur) because it does it in the menus!
But I agree that seems to be the trend.
I did some messing around with Quartz Debug and have found that the blurring is done by Quartz Extreme and not Core Image. Everything being said in this thread leads me to believe there may be a driver bug with the Nvidia 5200 series for OS X because it's clearly capable of these effects.
Picture Left: QE disabled
Picture Right: QE enabled