I have a Pfaff 1471 that I bought new in 1986 with the IDT and I am still sewing on it every day I sew. You do not need a walking foot with the IDT, it does the job. I sew nearly everything with the IDT engaged and would not sew without it. I just looked at a 4.0 today and would love to have one. It has so many nice features, but it will have to wait.