Other Factors Related to Workspace
I also need to mention that the screen resolution, the monitor size, and the actual number of monitors being used may also affect how you choose to customize your workspaces. Typically, with one monitor set up, you'll find yourself constantly moving palettes around your screen, looking for the one that you need (which always seems to be hiding behind one of the other palettes). Even working on a 20-inch monitor with a fairly high resolution (1024x768), you'll find yourself cramped for room on your screen.
Many designers these days work with two monitors, typically 18 inches or larger. This allows them to keep all of their tools and palettes open on one monitor while working on the actual image on the other monitor. Granted, not everyone has that luxury (or budget), but if you can set up multiple monitors, I highly recommend it. You'll find yourself concentrating more on your work and less time on moving and shifting windows around.
Recently, I was lucky enough to test out a triple head graphics card from Matrox. Their new Parhelia is unbelievable for working in Photoshop. I set up three monitors and was at no loss for available work space. One thing to look for when choosing a graphics card is its capability to allow you to work on any screen equally. What I mean is that some dual and triple display cards force you to keep your tools on one monitor and your image on another. Only what they define as the primary monitor can produce the graphic detail correctly, thus forcing you to be locked in a certain layout. The Pahelia card did not restrict me at all. I was able to move my image around on any of the monitors without a loss of detail or a slowdown in generating the image accurately.