The reason SBT became so popular is because at that time Metallica had gotten so HUGE that any song they released off TBA would've been a hit for them. It's one of those songs that reminds a lot of people of how they got into them, that's all.
But to call it their most boring song while NEM is on the same album is a bit much. NEM is easily one of the most boring songs songs they ever did. I remember when the album came out and I first listened to it. I was liking everything then NEM came on. I just kept looking over at the stereo with this inqusitive look on my face. I remember thinking to myself when I first heard it "Really Metallica? You actually thought this song was worth recording?"