What's new in Adobe Photoshop CS4 that will appeal to photographers:
1) Pressing and holding the "zoom tool" will smoothly zoom in and out. Zooming from 3% to 1600% will be lightning fast and smooth.
2) Clicking and dragging the "hand tool" will be as smooth as glass. It seems to float - even after releasing the mouse click.
3) Documents could now be opened via tabs.
4) For a group of layers, you can select "edit>auto blend" and the layers will be blended to reveal only the sharpest portions of them, mimicking a sharper depth of field.
5) You can now select all of your adjustments from within an "adjustments panel", and Photoshop CS4 takes care of making the associated layers and masks for you. The corrections that are made are non-destructive and sit in the "layers panel".
6) "Vibrance" is now an available correction within Photoshop CS4, a la Lightroom.
7) Now via a "raw dialog box", you can apply gradient filters to your images, and add post crop vignette to them, and the new Adjustment brush allows you to make a variety of corrections on specific sections of the image.
8) New "on-screen image controls" for hue/saturation, curves, and black and white, allow you to make changes to the image simply by clicking and dragging - up, down, left, or right - on the image itself. This is not unlike Lightroom's on-screen image controls.
9) "Content aware resizing" allows you to transform an image by by dragging the image and removing areas of information that are not important.
10) The dodge and burn tools maintain color relationships whiles brightening or darkening via new "protect tones" option.
11) Now with "Live brush preview", you can actually see what you are going to clone/heal inside your brush. Option/alt, toggles it off.
12) You can now extend depth of field by combining multiple images with different depth of fields. Also, "auto align" works better for regular pano or for images shot with wide angle and even fish eye lenses.
13) The "color range tool" can now be accessed from inside the "masks panel" and the new "localized color clusters" option prevents the color range selection from going overboard and selecting pixels in different areas.
14) Create your own customizable Photoshop experience in CS4 by creating your own customized panels with "SWF Panel Support and Configurator". You even have the option to embed video in the panel for tutorials etc.