The first time I saw a quilting teacher "tear" her fabric, I was astonished, but tearing does give you a true straight edge. However, tearing will leave "feathers", so I prefer to cut my fabric, unless I am using only a partion of a larger piece. Also, if you cut a small triangle off each corner of the fabric before you wash it, you cut down on the "feathers" of threads, and yes I always wash my fabric before I use it. Then when I am procrastinating about starting a new project, I spritz the fabric with a bottle water sprayer and iron away while watching my fabric movie or TV program. You'd be amazed at how quickly it goes when you are not focusing on the ironing.