It shouldn't be called the trusted traveler program since they ask you the same questions as they would in regular line. There is no "trust" exactly in the traditional sense of the meaning. If they really trusted me, they wouldn't to be asking me who I am meeting, why am I going there, why am I going so early, looking in the hood of my car and in the trunk etc..( yes these all were asked and done under nexus, and i'am white guy with no unusual names)
Therefore, the reason it's faster isn't because you're a trusted traveler, but because people without nexus can't use those lanes, and therefore it's less of a line up. I find it's most effective when crossing by vehicle due to the dedicated lane. At the airport i find it to be effectively useless with few exceptions, because regardless of when you get in through a regular lane or Nexus lane, you still have to wait at the gate so everybody will still leave at same time. The exception is if you are somebody who comes 40 min before a flight,( if you are a last minute type of person) I suppose you have that option where you can last minute everything knowing you have nexus and don't have to wait with other homo sapiens and talk about the raptors/maple leafs and the shitty 401 traffic. (You know who you are... don't get me started on crying kids in line.)
The other exception, if it can be called as such, you might feel like it's faster, and if you're a "feel" type of person, this will at least give you the impression that you saved time and that will be good enough to justify having it. (Think of people who gamble at casino regularly, but then get "free" rooms. They already paid for those rooms and then some through endless gambling, but enough time has passed and they feel like you are getting a free room and that's good enough for them)