James, I have used this type of vise before. Essentially, it allows you to clamp up a corner of the picture frame and nail it together after you have glued it. It works well as long as you have cut the miters at 45 degrees. Since you are doing one corner at a time, you won't know if the sides are the same length until final assembly. As for the price, you'd have to look and see what the comparable imports go for. When I used one, I found out that it works best on shorter pieces. If you get much over 18" on a side, you will need to rig up some support for the far ends, or else everything flops around and alignment gets difficult.
Roy G