Like a well-fed amoeba, the 2007 Adobe Photoshop has split in two, producing its own child, Adobe Photoshop CS3 Extended. Think of Extended as Photoshop heavy (as opposed to Photoshop Light); it's basically the same application with some extra capabilities and bundled scripts targeted at video postproduction tasks, 3D texture-map editing, and scientific image analysis. At about $300 more than Adobe Photoshop CS3, it is a significant upgrade decision--one which I'm not sure will entirely satisfy the relevant users.
Adobe seems to use Extended as a dumping ground for everything it considers "other." What else could explain a product that supports both DICOM image stacks and texture-map editing? Though it boasts some useful capabilities, Extended seems like a tentative, uncertain step toward addressing each segment of Photoshop's heretofore tangential users. It's Photoshop with multiple personality disorder: one scientist, one architect/engineer, and one game designer/video producer.
Furthermore, whenever a company draws a market segment line between two versions of a product, the placement of that line becomes somewhat arbitrary. In the case of Photoshop standard versus Extended, that fuzzy line cuts across its 32-bit high-dynamic-range (HDR) imaging support. The standard version has Merge to HDR, which allows you to take bracketed photos and combine them to attain a broader tonal range. But for HDR-capable brushes and support for adjustments like Levels, Hue, and Saturation, you'll have to bump up to Extended. Even there, the Magic Wand doesn't work in 32-bit mode (although, oddly, Quick Select works), nor do Curves and the new Black and White adjustments (you can still use the Channel Mixer, however).
Its new measurement tools, which let you drop counters on an image as well as measure and record the distance and angle between two points, are faster to use than previous manual methods, but they feel a bit undercooked--as if Adobe is waiting to hear from users before putting them back in the oven. For example, the count tool doesn't even let you change the size or shape of the markers it drops, or provide an option to let them scale when you zoom. Despite the many potential applications for recording color values in an image, the color sampler tool still only supports four data points, and you can't record the measurements.