Just did a class on this on Saturday. I borrowed the book and even though I had the 'tool' didn't use it. I don't think I'd do a quilt like this. A wall hanging,table runner, table topper, or purse - YES!
I does take more material than just doing a QAYG. Like the rag quilt you need extra material around the edges. In the rag quilt you sew a wider seam then cut into this seam allowance to fray the edges. In Cotton Theory (CT) you use the extra fabric to fold over and then sew it using your fancy stitches.
The finished CT product is not smooth or flat due to the folding and sewing. I know several quilters have made table runners, placemats, and such and liked the effect.
ali