Help! Confusion over so-called "revised" Wizard and Glass

Amazon's listing of the 2003 Signet edition looks like this: Wizard and Glass (Dark Tower #4) (Revised Edition). Is this a mistake? Because there's nothing about any revised text on the copyright/info page that I can see. I'm thinking about finally reading these and I want the most recent versions, but besides the new introduction I can't find any evidence this differs from previous editions. Anybody know for sure?

I know that he revised the first book from the 1980s text and he may have done other books, too. Maybe go to some fan sites and ask.