Not only are fingers very low-resolution input devices, but they're opaque and attached to a big meaty human hand, obscuring your view of whatever you're manipu

Not only are fingers very low-resolution input devices, but they're opaque and attached to a big meaty human hand, obscuring your view of whatever you're manipulating. The visibility problem worsens with multiple touch, since you may have both hands between your eyes and the screen. When manipulating something small or fine on the screen with a coarse fingertip, it can be difficult to know if you actually have a 'grip' on it, or precisely which face/edge of it you're pushing/pulling. (In the physical world, we receive tactile feedback through our fingertips that helps us grasp things.) Frustrating, since much of the promise of multi-touch systems is in modeling physical-world manipulation. Also, PC touch screens can quickly get greasy, worsening visibility even when your hands aren't on it. I developed for a PC-based multitouch environment last fall; by the end of a debugging session on the test system, its screen would be difficult to read. If I ever do that again I will buy silk gloves and learn to type in them (and hope that they are fine enough not to block input on a capacitive touchscreen).