I think perfect seams are a combination of accurate cutting and finding the 1/4" "spot" on you individual machine. I have 4 machines, and ALL of them have a different needle placement and guiding line. It takes some time and lots of sewing on scraps to find it, but once you do, write down the needle position and mark the 1/4" line on your machine. Just like any other quilting skill...practce, practice, practice.