When I did the NEXUS (instead of Global Entry) the application I hear is very similar. The interview was at the Ambassador Bridge in Detroit (or the Blue Water Bridge) instead of at an Airport. About 25 minutes by car E of the airport. Interview was short - just ask them to enroll you in Global Entry too - it's no extra effort for you or the ICE agent, they just check a box in the computer.

Nexus is actually designed for US <-> Canada crossings and SENTRI is for US <-> Mexico, but both work for Global Entry. Nexus gets a little card (don't know if Global Entry gets one) that allow you to use the short lines at the Border crossing to/from Canada.

Best $50 I ever spent.