The 2nd-to-last slide[1] compares the IEX "speed bump" to other anti-HFT measures: "Ingenious, eliminates sniping. But, only works while IEX is small relative to the rest of the continuous market (free-rides off price discovery elsewhere)."

1. http://faculty.chicagobooth.edu/eric.budish/research/HFT-Fre...