The design of the DualShock 2, which available in a variety of colors for $25, is essentially the same as the first iteration of the controller, the one that Sony bundled with the original PlayStation. The only discernable differences between them are the black controller cord and the small DualShock 2 text printed on the top of the controller. The layout is identical: four face buttons, four shoulder buttons, two analog sticks, a start and select button, and one control pad.
Unlike the original DualShock, which included only analog movement in the control sticks, each of the buttons are pressure sensitive--the harder you push them, the stronger the action. For instance, if you press the X button all the way down in Gran Turismo 4, your car will accelerate at a faster rate than if you pushed it down slowly. Lightly tap the button while playing Madden NFL Football and your quarterback will lob his pass; pressing it quickly and he'll toss a bullet. As a result, control for a significant portion of the PS2's games is easy to manage, and the ones that aren't are usually the fault of the software developers. Really, the only design fault with the PS2 controller is the segmented directional pad, which makes control a bit difficult for the system's 2D fighters.
Perhaps the only other complaint that could be made about the DualShock 2 is the wire that tethers the controller to the system. Microsoft essentially replicated the DualShock 2's design while removing the wire and produced perhaps one of the best wireless controllers ever for the Xbox 360. The similarly designed, motion-sensitive controller for the forthcoming PlayStation 3 will also go wireless, though it comes at the expense of the DualShock 2's amazing rumble capabilities. Time will tell whether Sony is able to implement all of DualShock 2's great features in the PlayStation 3 (Sony says the motion sensitivity interferes with the rumble, though most believe the company's lawsuit over the technology is the reason). But for now, you can enjoy a massive library of games with one of the best controllers around.