We use the Dowel Max in our shop. You can watch the videos on youtube to see how it works. What you probably want to hear from me is how accurate the thing is. The Amazon reviews are correct. This jig is the real deal. It is 100% accurate. Simple to use and dead accurate every time.
The thing it does not do so well is positioning that first dowel in exactly the right spot. When joining two pieces of equal thickness it doesn't matter if the dowels are closer to one surface than the other. Positioning the dowels when the two pieces are of different thickness is much harder. The dowel max will still get the job done, but it is not the end-all tool in this category.
We use the Dowel Max in limited-run production. It has held up well so far. I wish it was a bit cheaper.