Wacom eschews the glossy surfaces and clicky buttons for a rubberized texture and membrane keys. The active area, delineated by the illuminated crop marks, is actually the same size as its predecessors', but the Intuos4 had a larger bezel that overlaid the unused portion of the tablet area.
The buttons and touch ring operate the same as before, but they're now a seamless membrane design, with bumps so that you can distinguish them by feel. Unlike the Intuos4, they don't have the context-sensitive LED labels, which have been replaced by a heads-up display that reminds you of the mappings. I've got sloppy elbows (I set them down everywhere), so I frequently pull up the HUD when brushing the tablet.
The driver hasn't changed substantially except for the addition of Touch settings. As with the other input technologies, you can create custom Touch settings for individual applications, which is nice. You still can't share your customizations between computers.