I am currently liking my Nexus card – it was $50 and you had to do an interview, but should last 5 years – and lets you go to a separate queue. The interview was straightforward – after doing the personal information check, I literally chatted for five minutes about my work and random genetics things. If you wear contacts like me you should bring a case though since you have to take them out to do the eye scan (you can come back later, but I ended up just putting them on a sheet of paper for a couple minutes since I found my solution but no case)
When doing online check-in, you do have to put the number into each airline separately to get the TSA Pre-check noted on your tickets (thanks Kristin!) – usually there’s a spot like “Preferred Traveller Number” next to the Rewards membership number you can fill in.