I recently bought this but I'm not very impressed with it. The bit can touch down in quite a range of locations using this device. Certainly several millimeters of lateral play.

We use 2 speed squares, and an 18" bit. Arrange squares 90 to one another and sight up the spaces between the bit and the squares, and GO!

huge fan of millers falls because of flexibility and adjustable depth stop. our crew has 9 boring machines and we actively use 4 - a couple of swanns. its nice to have them dedicated- w/bits and stops for standard tasks- brace pockets etc.