Without filler rod, the welds don't look undercut
Granted, the perfect fitment of the base metals does help.
We always get perfect fit, Riiiiiiggghhhttt.
Although it DOES look slick, at that price, MIG welders are going anywhere soon. It may weld 4 times as fast, but it costs 10 times as much. And he said it used less energy. How much less? It would have to be a lot less to be able to tout that as a major advantage. Like I said, it does look slick, but I am not real impressed.