Gradients: Its easy enough to do this with images. But Scalable CSS Gradients would be a cool idea too.
Multiple Backgrounds: I would say this is realy a must. This is realy my #1 wishlist item for css3, besides all the selectors.
background-origin and background-clip: never used them.
More atomic background positioning: if i understood it correctly, why not. would definitely be usefull.
border-radius by corner: this should definitely go in.