If what is being proposed is the same CBP pre-clearance we have in Canada it is a desirable system. We pre-clear U.S. Customs and Immigration in Toronto before boarding the aircraft and are treated like any other U.S. domestic flight thereafter.
Having entered the USA hundreds of times via this system it is a faster and more positive experience than the times I've come into the U.S. from Asia, Oceania or Africa. It also means if you are denied entry you just go back home the way you came instead of having to arrange an immediate return flight.