An escrow service requires an arbitration process. Any escrow service without an arbitration process is nothing more than "Hey Bob, will you hold my wad of cash for a few days?" And you don't know Bob. And Bob might give your money to the Red Cross if the seller tells him to.
+1
OT and likely to be controversial. I believe ADR/Arbitration should operate with no emotion whatsover, no conflict of interest (or recuse), incentive to rule based on contract and evidence alone and a disincentive to rule on fairness. I don't know that all of those areas can be covered, but close to it I think is possible.