Yes... your point about speeding up the checkout is extremely valid. The easier it is for shoppers to conclude their purchase the better.

Perhaps the checkout_confirmation is a superfluous step. It would be better for zencart to "sense" if any important info had been ommitted and ONLY display an alert if this was the case - otherwise it should conclude the transaction.

What you say reminds me typically of government websites (UK in particular) where progress through a transaction is so tedious...

"Are you sure you want to continue...?" (I click "yes")

Next screen "Please confirm that you are ABSOLUTELY sure you want to continue..." (I click "yes")

Next screen "There's no going back after this? Are you sure, sure, sure?" (I click "yes")

Next screen "If you click yes now, that's it... please confirm that you have read the terms and conditions first" (I click "confirm")

Next screen "So let's get this straight once and for all... You actually want to send your data over the internet. IF you are certain to the point of death, click Continue" (I click continue).

Next screen "No going back after this step... Are you sure?" (I abandon website)