i use them to focus on weak points. helped me learn to lockout deadlifts, since i got used to the extra resistance at lockout. i bruise my hips now by slamming them into barbell now, hahaha.
i also use them like the pulleys in commercial gyms. ive done rows, flyes, and other isolation type assistance movements with them.
i recently started dangling 10-15 lbs on each side of a barbell from bands, with maybe 95 lbs on the bar (so 125 total or so, nothing heavy) and doing squat variations. you hit the hole and the weight bounces around, forcing your core to work really hard to keep its balance. ive noticed i feel much more stable squatting after adding this to my workouts. bands are limited only by your imagination, but i would never use them as part of my ME training.