The first improvement you’ll notice is in start-up times. Obviously absolute performance will vary depending on the specification of your system, but on my PC (Windows XP Pro, Intel Core2 Duo 1.8GHz, 2GB DDR2, SATA2 HD) starting CS3 after re-booting the computer took just over 18 seconds, against 22 seconds for CS2, but it is in subsequent start times that the biggest improvement is noticeable. Shut down the program, do something else for a while and then start it up again, and Photoshop CS2 will be up and running in about seven and a half seconds, which is amazingly fast for such a large and complex program. However CS3 more than halves that time, re-starting in just 3.2 seconds. Further performance tweaks include improved compatibility with dual-core processors and Windows Vista.
The improvements to the interface are both cosmetic and practical. The shape and appearance of the palette and tool bar windows is now more in line with the Windows Vista look, with neat semi-transparent frames rather than the rather stark and blocky look of earlier versions. The messy and unhelpful palette dock, first introduced in Photoshop 7.0, which allowed surplus tool palettes to be stored like index cards with visible tabs, has been dropped. Instead the left-hand column of palettes now comes with a customisable row of button icons. Infrequently-used palettes can be added to this panel as extra buttons, and unwanted buttons can be dragged off and deleted. It does the same job as the palette dock, but is quicker and easier to use as well as looking a lot tidier. Palette snapping to the right of the screen has also been improved, with multiple options for arranging and using palettes.
On the other side of the screen the tool palette has been tidied up, and now defaults to a single column of buttons, although it can be switched to a double column with the click of a mouse.