In my book, the walking foot is worth its weight in gold. I started using it just for quilting things like placemats. Then I tried it for sewing thicker fabrics like denim or upholstery. Then I started using it for other things. Now I use it as much as I use my regular foot!! If you could test-drive a machine with a walking foot on several different kinds of projects, that would help you, but just sewing a piece of plain fabric in the store isn't going to tell you much.
P.S. I have a Bernina 153 which I bought in 2001. It came with the walking foot. Before that, I had an old Kenmore machine with a generic walking foot. The difference was astounding!!!! :)