I own one. It works fine for putting binding around straight or rounded items of 1-2 layers. It does not work with items with square corners because you have to come back on(fold over) the bias on a corner (at least I haven't figured out how). Also, unless you have a very thin batting it is very hard to use with a quilt as it is difficult to get and keep the quilt between the top and bottom areas where the bias goes and catch top and bottom of the bias with stitches all at once. Works better if you sew the bias on the quilt and then use it to flip the bias and then sew it down as you would just with a regular foot.
I have used it to make the arm holes of pillowcase dresses for Haiti girls.