I do strive for the "perfect" (?) 1/4" seam, and I'm usually OK with making the block come out the right size. However, I attended a lecture by Mary Ellen Hopkins years ago who told us that we should use what works for us, using a 1/4" foot on the machine, moving the needle, etc., etc. and she called it our "Personal Private Measurement" or something similar, she does mention it in her books. I learned a valuable lesson in the 1/4" seam when a friend and myself worked together to make an Oceans Wave quilt for the church raffle quilt that year. She did one section of the block and I did another. Well, I have to tell you that our 1/4" seams were not the same, so I had to make adjustments when I was putting the blocks together. It wasn't off by much, but enough to be somewhat challenging when piecing the top together. That said, using the same machine when piecing a quilt top, makes for a happier quilter at the end of the day.