If you're familiar with earlier versions of Photoshop, the first thing you'll notice is a marked improvement in the appearance of the interface. The basic default layout hasn't changed too much, so you'll still find all the familiar tools in the usual places, but now there is far less wasted space. The various windows and palettes fit together more closely and dock more tidily, and also re-size intelligently, so that information is always visible. If you have to reduce the size of the Photoshop window, the interface elements automatically re-arrange themselves to avoid overlapping, and return to their original positions when the size is restored. If you're using Windows Vista with transparency enabled then some parts of the interface are also semi-transparent, which doesn't add much functionality, but it does look nice.
The main work area now uses tabs to help keep your work organised. If several documents are open at once, a row of tabs across the top of the work area allows quick changing from one to another. As well as this the interface also has a new menu for multi-document view options, arranging open items in a range of different patterns, rather than just the "tile vertically" or "tile horizontally" or previous versions. Images open in the main work area also now have a nice drop-shadow around them, which can be useful for distinguishing grey tones on the edge of an image from the grey background.
One completely new addition to the interface is the Adjustments panel, which in the default workspace configuration is found in the palettes on the right of the screen. This palette provides a quick way to apply one of Photoshop's most under-utilised tools, the adjustment layer, a feature first introduced with Photoshop 4.0 in 1996. Adjustments to a wide range of image parameters and effects can be added as a separate layer, and can be independently altered without affecting either the other adjustment layers or the original image. Non-destructive editing is always better, since it preserves the data in the original image and is therefore completely reversible. The layers are saved as part of the PSD file format, and so can be altered even after the file has been saved, closed, and re-opened.
The Adjustments palette contains options to create adjustment layers for the usual parameters, including Brightness/Contrast, Levels, Curves, Exposure, Hue/Saturation/Lightness and Colour Balance, but also adds new adjustments, such as Vibrance and a very useful Black and White function, in which the lightness of various tones can be adjusted in a monochrome image. This is similar to the traditional way of making monochrome images in Photoshop, but is even more versatile. I may have to re-write that tutorial to accommodate the new function.
Alongside the Adjustments panel is another new feature, the Masks panel. This helps to simplify and streamline another under-used Photoshop filter, its ability to use pixel and vector masks when editing an image. Using this panel, selected areas can be quickly converted into layer masks, and can then be adjusted using simple sliders, or created from a colour range.