Steve Ansolabehere has written this fascinating piece on Slate about initial findings in a survey about voter experiences in 2006. A snippet:

The study’s most unexpected finding is that half of the survey respondents said they were required to present photo ID, even though in 2006 the laws in only Indiana and Florida required this of all voters. The data show a stunning lack of uniformity in the use of voter-identification requirements. Voters in Midwestern and Western states were asked to show photo identification at approximately the same rate (40 percent to 45 percent), but poll workers asked for such identification very frequently in the South (65 percent) and rarely in the Northeast (22 percent). Even within states, the application of the rule varied greatly from region to region.

Another finding: “African-Americans were asked to present photo ID more often than whites–54 percent of the time versus 46 percent. On average, African-Americans also had to wait somewhat longer in line to vote, though the waiting times were very short for most people.”