Living in the area, this airport is really best if your destination/origin is within a comfortable drive of the airport (personal or rental vehicle). There are many train connections in Trenton, but once you factor in the taxi ride plus either SEPTA/NJ Transit, might as well use PHL or EWR. Sweet spot includes Bucks County PA, Mercer County NJ (including Princeton, all the companies along US-1), and southern parts of Hunterdon and Somerset Counties NJ.

Let me know if anyone has any questions about the airport or area.