Both the article and the original "flash boys" book make a compelling case about how HFT can in some cases be used to virtually front run orders. I personally don't understand the system enough to prove or disprove those claims.

I do think that an exchange that places less of a premium on speed like the IEX is a reasonable way to let the market itself evaluate the benefits of HFT. If the exchanges with HFT do provide a better value in terms of liquidity or price then the IEX will suffer as it provides an inferior product. If IEX flourishes then it is providing some value to investors. Let investors vote with their dollars

Personally, I think that IEX becoming an exchange is a done deal and have absolutely no problem with that. What causes me concern (and many of the opposition letters point to this as well) is that we don't want IEX becoming an exchange to be seen as some sort of referendum on HFT and specifically how HFT impacts individual investors.

The biggest reason for that is that I believe that individual investors are dramatically better off in a world of cheap wholesale market makers than they could ever be being dumped in the shark tank of hedge funds that is IEX. I have no problem with institutional investors who want to take advantage of IEX if they think that is best, they are professionals and that is their job to figure that out (though I wouldn't want to be invested with an institutional investor who wanted to trade on IEX because I would be suspicious of their competence). What I find really scummy is the marketing ploys of IEX to try to frame this as in someway good for individual investors.

[edit] Obligatory, please if you've read Flash Boys read "Flash Boys: Not So Fast". No one who understands/has worked in electronic trading that I've met believes that Flash Boys is anything but misrepresentative and bad.

Neither the article nor Flash Boys makes that case.

The article doesn't make that case because Levine is semi-famous for repeatedly calling Flash Boys into question, particularly with regards to the book's claim that HFT allows "front-running".

Flash Boys doesn't make that case because it's an incoherent mish-mash of different arguments that don't add up to a definition of "virtual front running", let alone an argument that it's happening.

> and the original "flash boys" book make a compelling case

Except it didn't, it merely showed that the author has no understand of what HFT is. Flash boys is full of hyperbolic bullshit that may sell books but shows no real understanding of how the market works. He misuses the term front running (which is illegally using knowledge of your clients positions to trade ahead of them) and applies it to being a faster speculator, which is in no way front running. The guy quite simply doesn't know what he's talking about.