I use them for sewing all the time. Love the effect (can mimic a coverstitch hem quite well) and the little "bump" in the center is usually on knits or single layers of fabric. I don't have any issues when stitching on multiple layers. However, a friend did her quilt using double needles and she was not expecting the zig zag on the back! She was very disappointed in the look of the back. I don't think she had sewn with them before, so she was surprised. I would lengthen the stitch as much as possible without going to a basting stitch, because two rows are pretty strong and the zig zag on the back would be a bit larger and less tight looking. It can be a pretty effect.