I'm not sure what you mean by that. OS X was the first OS to do it's interface in 3D, years and years before Vista did. And even now, Vista doesn't seem to do anything useful with it.
First off, Usefulness is NOT the point eyecandy is the point.
Well the things I like on compiz are
- smooth zooming (I press ctrl-alt and the scroll wheel of my mouse to zoom wherever I want on the screen)
- wobbley windows (windows are like jello when you move them... rather than like paper)
- "bouncy" menus (very hard to describe this... its like menus seem to be made of jelly or something)
- superior transparency
- inside the cube feeling for switching virtual desktops (does osX even have virtual desktops?)
- Water effect when moving the mouse (its like your monitor is a pool of water that your mouse is lightly touching)
Its just eye candy stuff... but it really adds to the experience. Whatever Tiger has, I expect Leopard to be clearly superior (but also need better graphical hardware).
osX may already have these things. My point is that 3d desktops are perhaps more graphically intensive than what the 950 can handle, but not nearly as graphically intensive as games.
the 950 is a very poor graphics solution.
For what it counts the ATI 1600 is inferior technology now too and needs to be updated... when Apple first released these cards were mid-high range. Now they are low range.
The 3100 would give "acceptable" graphics capabilities, and I would feel assured that Leopard would run adaquately. I am not assured with 950, and wont be buying a MB until I see how Leopard runs on it (if it runs fine, I'll buy a MB with 950)