Not sure why you had long setup time. I had one of these jigs for about a year, and it is by far the easiest way to setup and cut box joints. I sold mine just a few weeks ago, as I have found less use for it. As well I have the full Incra set, for more than just box joints. The only reason a joint would come out bad, is by user error. It really is foolproof. Perhaps the knob to lock it in place was not fully disengaged when you went to set up for second and so on cuts. Or if its from bad cut, then that would not be from the jig, rather your blade (or bit).
It really is foolproof, even if you wanted variable spacing, it is by far the easiest jig I have ever used.
The full Incra LS positioner, is a different story, it does take some setup time; but after it is setup it also is very effective at being incredibly accurate.