I have the Stots/Milescraft templatemaster. Very similar to the Keller, for through dovetails. It is very easy to setup. Once the template is set on the block, you are done. You can add T-tracks, hold downs, stops, etc.The depth of cut is also easy to set. As Phil pointed out, you can line it up any way you like. So far I have been very pleased with it.
I have cut dovetails on the table, and freehand with this fixture. Small pieces are easier on the table, where as longer pieces are easier cutting freehand with the stock held in a vise.