It's a case study of only 8 coffee shops in the Boston area. Boston. Cambridge, and Quincy Metro is about 90K shy of 4.5 million people. I don't think you can make any type of judgment without broadening the survey to include 20 - 40 more shops.
The web is eating this up for some reason. The Nov. 10th Slate Magazine article of the Boston coffee shop "stake out" shows up in numerous consumer and informational websites. The study was conducted by an economist (female), who claims that female customers had to wait longer than male customers for service in coffee shops.