It has always surprised me that this type of foot is called a SITD foot. It's not for SITD over a quilt sandwich - you would need to use a walking foot so the fabric feeds evenly (as others have already mentioned). It would be incredible if they could make walking feet with some kind of "guide blade" like this. I would buy one in a heartbeat!
I do have one of these feet and use them for straight line stitching while piecing. They are wonderful for that.