it's a one shot deal.
Say you want to make matching tees for your family, or a pack of cub scouts, or something. With freezer paper stenciling you'd have to make (and cut) new stencils for each one-- not exactly practical.
Enter craftgrrl's cheap screen printing tutorial. She uses embroidery hoops, sheer curtain fabric, and modge podge to make her "screen printing" apparatus, which is 1 stencil you can use over and over and over again. I haven't tried this yet, but you can bet your bottom dollar I will.
Don't worry though, freezer paper. I'm not ready to give you up yet-- too addicted to peeling you off a painted shirt. Ah, the satisfaction.