I have one and love it. There are two sizes -- 12" and 18". If I'd known about the 18" when I bought the 12", I would have definitely bought the larger one.
They have also come out with one that is gridded for 2-1/2" strips. Great for making your own jelly rolls and for cutting binding. I haven't gotten that one yet (it's a little pricey, even with a 40% JoAnn's coupon).