Unfortunately as Sing-along has noted, only for US citizens/legal residents. I have started using the US Resident lines at gateway airports when these look shorter than the Visitors ones. Never had a problem with an agent when I get to him or her. That said, i do think it is rather stupid to have so many different programs that cannot be integrated or interchanged. I suspect the problem with NEXUS is that it has become more widely used for those who live near the border and do regular driving across, thus diluting the pool and loosening security in the eyes of the Americans.