One of my birthday presents was an Edge Stitching presser foot for my Pfaff, what they call a Stitch-in-Ditch foot. I was excited at the thought of almost effortless straight line in-the-ditch quilting--with IDT! (built-in walking foot)
I attached the new presser foot, checked settings, and started sewing. Sadly, the guide causes a 1/8" gap between the seam and your stitching. So disappointing! I played with it some more and always had the same problem. The foot is being returned.
Then I remembered that I'd had good results with the Blind Hem (aka Overcast) foot that came with my machine. The wire that runs under the foot sits in the ditch very well. Depending to which side the seam allowances are pressed, I steer with the seam centered on the red adjustable guide or approx. 1/8" to the right, centered on the guide's "blade."
The edge stitching foot I'd originally seen was an older version (L), the new version (R) is the one I tried.
I wonder whether the old version stitches closer to the ditch: the blade appears thinner. It allows for adjustment of needle placement and use of decorative stitches. The new version has many handy 1/4" markings. Both are IDT compatible.
I haven't been able to try the old version, though, and am doing fine with the blind hem foot.