i hate to break it to ya bob, but ach transactions are not faster than eft/debit. nowhere, near as fast, really. as a matter of fact, there's new ach regulations going into effect next month that ramp up the availability of same-day ach debit transactions. that means within a few hours, ach debits can hit your account, if you conduct the tx at the correct time of day and the vendor/merchant participates in same-day ach. however, ach transactions do not post (and won't for the foreseeable future) in real-time.
not only do debit transactions post (preauthorizations) in real-time, but they even check available balance prior to posting the preauth.
conclusion? you're full of shit. i know, i'm surprised as hell too.