I have a data Speedtest app on my iPhone and I used it the other day when it occurred to me that the free Wifi at Panera and Barnes & Noble seemed slow.
That's because it was.
Keeping in mind that my home Wifi performance is 14.24 Megabits download and 1.90 Megabits upload, I got these results when I checked the free Wifi:
Panera - .99 Megabits download, .97 Megabits upload
Barnes & Noble - 2.56 Megabits download, .32 Megabits upload
I haven't checked anyplace else, but I suspect other businesses - like Starbucks - aren't significantly better.