In particular it helped me to understand some of Paul's more difficult passages. I tend to go pretty deep, and Paul's writing is amazingly deep. The NLT would help me see the organization of his thoughts, or really, the Spirit's teachings, so when I returned to the more literal, or to the interlinear, I could follow it better. Romans 8 is a great example for me. The first 15 or so verses were very difficult at first for me to really get a handle on them. The NLT translation there is, to me, more of a summary than the full teaching, but still helped.
I don't use it anymore, mostly I just stick with the KJV. And I love my Holman version of the King James. It has few notes, but they are always on target!
Much love!