Originally Posted by BigFlyer

Whether pre-clearance is potentially good or bad depends on whether your destination is at the place where you enter the US, or you are connecting at a US airport.

If your final US destination is your airport of arrival in the US - then preclearance sucks. Without pre-clearance, you do not have to budget extra time for US customs/immigration. You land in the US, you go through the formalities, and you are done.

With pre-clearance, you have to get to your departure airport early so as not to miss your flight - but, you don't know how long pre-clearance will take, so you have to leave extra time, which means that you spend time waiting in your departure airport after clearing that you would not spend if you did not have to worry about pre-clearance.

The only folks who have a potential advantage are those who are connecting in the US, as they can schedule a shorter connection time.