Now I have had a few pints, but I don't get this. The other exchanges are still buying and selling faster than 350 milliseconds, no?

Sure, but not on IEX because that delay is built into every trade.

Right, so you're only protected against HFT on the IEX exchange, but that's why none of them will use it..

I assume it's not for HFT but everyone else that wants to be on a level playing field. All things being equal, it seems like a pretty attractive exchange for the rest of the traders.

you are correct and that is why the stock market is a scam

You'd think that, wouldn't you? The interesting question is how it managed to increase stability of the entire system.