I also have the Janome 6600 and it has Acufeed which is the same as the Pfaff's IDT. I have a 'walking foot' with a 1/4" guide that I use for piecing anything on the bias, long strips of fabric across the WOF for example, when making a bargello or sewing strips to subcut for speed piecing, and for sewing on long lengths of single fabric for borders. It helps enormously with puckering and stretching (I also reduce the foot pressure a tad). Whether she needs one or not will really depend on the kind of piecing she does and the kind of fabrics she works with, whether she personally can justify the investment. But I disagree that a walking foot (or the equivalent, Acufeed, IDT or whatever) is 'only' for quilting. It's purpose is to alleviate shifting of layers so ANYWHERE this may be an issue, it's the tool for the job.