I've been using the Trap bar for over a month now. My lower back is pretty messed up. This implement has been a godsend. (Aside from the unrivaled reverse hyper machine)
If you have lower back issues, pay attention, movements you could not do before may be a possibility.
Some suggestions:
1. Great for deadlifts - regular, hanging, Romanian etc. I find my lowerback in a better position, and getting great benefit. I keep everything here at higher reps. Get the blood in, do some work, you will see some results. If your lower back is good to begin with, by all means hit it hard with low reps/heavy weight. Just don't be stupid. Great for legs and hips.
2. Upright Rows - good variety. Arms seem to be in a better position.
3. Bent over rows - Excellent hand postion, will be working this in soon.
4. Of course shrugs.