The problem that I see with flat rate charges is that the mechanics get paid the same for the job regardless of how long it takes, thereby giving them the incentive to "blow it out the door", resulting often times in shoddy workmanship and less than ideal repairs. Yeah, maybe they did install the timing belt properly but is the valve cover back on correctly? How many scratches are on your fender now that they didn't take the time to work carefully? "Oops, I forgot that fastener down there, oh well, the customer will never know............" "can't see it from my house......"