Holy shit, they've implemented "Stacking" of layer which will be tremendous for "Focus Stacking". This allows you to take various shots of one scene at different focusing distances. Then take all the images, bring them together and be able to bring more objects in focus than your camera will allow (at certain apertures).
A great use of this is to take a very close up picture of say, a flower. Even at a wide Aperture, some background will be thrown out of focus. You take two shots, one of the flower in focus, one of the background in focus. Throw it in CS4, stack them together and Photoshop will merge them images to create a final image that has the whole scene in focus. Will basically do what a Tilt Shift lens does!