Buried in the middle of an article extolling the virtues of touch screen voting, the author briefly points out that optical scanners perform better.

Osceola and Duval counties, both of which switched from punch cards to optical scanners, had discard rates around a quarter percent, compared to rates around a half percent for the touch-screen counties checked.

...Douglas Jones, a computer science professor at the University of Iowa who has served as a consultant to the Dade Elections Department, ... noted that discard rates representing even a half percent of all votes mean thousands of lost votes on a statewide scale.