One thing to note, while a trap bar CAN be easier on the lower back for some, it isn't necessarily guaranteeing it can't aggravate things. One of my nastiest lower back tweaks from my injured spot came from doing a farmer's handle deadlift, pretty much a trap-bar style lift, just with two separate handles held at the sides. In theory, it SHOULD have been easier on my lower back, but I still spent 3 weeks screaming every time I had to sit down or stand up
A decent device, but one thing's for sure, it's just one tool in the arsenal. Nothing wrong with using a trap bar, but for some, the carryover won't be much since it will definitely feel different as soon as you change back to a barbell!