This whole malleability fiasco has shown once again that zero confirmation transactions can not be trusted.
since its not practical waiting for 10 minutes for a payment to clear when buying coffee it seems to me that bitcoin will never go mainstream in physical shops.
any solution involving a third party to clear payments defeats the whole purpose of bitcoin.
any third party will effectively turn into a bank along with all the classical fractional reserve practices we have today.
IIRC I believe that BitPay runs a network of low-latency nodes that ensure that they can accept zero confirmation transactions. Anyone using BitPay is unaffected.