The ExpressKeys default to Shift, Alt, Ctrl, or their Mac equivalents; pan/scroll; display toggle, for jumping the cursor between two displays; Precision Mode, which shrinks the screen-to-tablet mapping to a smaller area, primarily for working in Photoshop CS4's pixel-level editing mode; Info, which brings up an onscreen cheat sheet of the current assigned functions; and Radial Menu. The Radial menu is a programmable onscreen menu for single-function operations, which comes preset for operations like cut, copy, and paste, as well as media controls for music and video. The four Touch Dial presets are auto scroll/zoom, cycle layers, brush size, and canvas rotation.
It's not immediately obvious how to use or program all the bells and whistles of the Intuos4. Even after I'd had a demo and watched the on-disc tutorial, it took me a while to figure out exactly how certain things were supposed to behave and had to turn to the documentation for help.
For whatever reason, the wider aspect (I don't have wide-aspect displays) and gently sloping edges feel more natural than the Intous3. The tablet does seem more responsive to lighter strokes, though only when directly connected to the PC. Through my hub, at least, there's always a slight delay sensing the stroke if it starts off with little pressure, and it doesn't register. I didn't have that problem when connected to a motherboard USB port. (Since I don't spend all day in Painter, I can't tell whether the response curve feels any different, though.)
For obvious reasons, the LED labels next to the ExpressKeys make them truly productive. Though it may seem an awfully mainstream application, I think a lot of users will find the media controls in the Radial Menu convenient; if not, you can reprogram them to your taste. While I'm not a big fan of using the RM for operations like cutting and pasting--it's easier to use keystrokes with my left hand, for example, even if the keyboard is off to the side--I found the menus great for launching Photoshop Actions. It would be nice if Wacom added the ability to load saved settings so that either the company or third parties could offer some presets; configuration, especially for multiple applications, can be a bit tedious.