I have used the seam guide both with my walking foot and with my regular foot. I love it. I also use painters tape on my quilts to mark lines sometimes...love that method too, but becomes a pain sometimes if I accidentally miss and stitch through the edge of the tape. As far as deciding how far apart my lines should be...I am a big fan of 2 inch quilting when doing straight lines, but I do vary from this depending on the size of the blocks. I have done straight line quilting anywhere from 1 to 3 inches so it falls out on the edges of the blocks and also down the middle (or if doing diagonal, stitching at each corner and through the diagonal middle of the block)