Has anybody used one of these?

Some body has. Freud came out with one of those IIRC about 14 years ago as an answer/alternative to the Festool Domino.

The problem is that Plate joiners/Biscuit cutters and the Festool Domino allow for a degree of misalignment.

This tool DOES NOT. If the placement for the holes for the mating half are not "PRECISELY" placed/aligned, the mating pieces/dowels will not fit.

No, I've never seen one and the price is certainly right. It seems that the drill separation determines the smallest joint possible. For example, mission style spindles would be a problem. As Leon says, the alignment has to be perfect for dowel joints. For a hundred bucks, it might be worth a try.

Be aware that that it comes with 8mm bits. You'll need metric dowels or new bits (it doesn't use a jacobs chuck, but rather a simple set screw to secure the bits, not sure how well that will support bits with a different base diameter).

They claim 1HP, which is pretty hefty for a handheld universal motor.

I don't see this a bigger lie than a 6.5HP shop vac. Universal motor ratings are meaningless all the way around. Much like "peak music power".

I do not see that so much as a lie as a way more than needed power rating.

No, it's a lie. 1HP = 746W. Do you really think a 20A circuit, with the vacuum's 16GA cord and 15A plug, is going supply 40A to the vacuum? BTW, the above numbers assume a 100% efficient motor.

FWIW I am talking about strictly the double drill dowel machine, not the VAC.

I am not electrical expert but I have several items in my shop that draw way in excess of 746W from an extension cord. My space heater comes to mind with 1500W.

Sure, but the point is that it's a universal motor, as is the shop vac. They're rated with the same lie. An induction motor (as would be found in a stationary tool) is rated properly. A loaded 1HP motor will use 746W (a little more because of <100% efficiency). Why the difference in rating methodology?