Have you ever noticed when you piece that even when the pieces start out the same size, sometimes the top piece ends up longer than the bottom? It's because the feed dogs pull the fabric forward while the foot pushes it back.
A walking foot definitely makes a difference because it's even feed on the top and bottom. When I did my first binding, I used a regular foot and what happened was the top layer of the binding (since it was folded over) ended up being pushed/stretched by the foot so that it didn't line up with its bottom part, and I ended up with a fold on just that layer. Walking foot keeps that from happening.
It's definitely worth getting. Try quilting a sample without the walking foot and then with it, and you should notice a difference.