I still wouldn't use it. Then again, I wouldn't take a "bill by the hours" contract. I stopped visiting RentACoder when it was clear that this was where most of the work was going.
If I tell you I'll deliver something for $xxx, by mm/dd/yyyy then I'll deliver it for $xxx by mm/dd/yyyy. It shouldn't matter whether it takes me an hour or a week, as long as you get it for the agreed price by the agreed date.
If I tell you I'll deliver something for $xxx, by mm/dd/yyyy then I'll deliver it for $xxx by mm/dd/yyyy. It shouldn't matter whether it takes me an hour or a week, as long as you get it for the agreed price by the agreed date.