I have one, and have used it lots. It is an incredible system, that does what it says it will do. I have shot at steep angles with no issues. I really cannot think of one drawback to the system. Yes, it is exspensive, but so will the scope, and rifle, you mount it to. It allows for faster shots in the field, as you are not looking at a Palm, or even at a chart. I had mine mounted on a Leupold scope, and shot it with several rifles, from 6mm on up. Sight it, set it, and forget it.
R.