I got a cheap batting once that was plain, purely awful. Ever since then, I've learned to take my backing (which is usually a bit oversized to start with) and roll it over the exposed batting on the edges. Then I safety pin it every 8-10" or so and it keeps the batting which likes to shed encased in fabric.
After that, no problems.
It works well even with better batting as it doesn't get caught on stuff while you're working with it.