I'm not seeing anything to get too excited about here. Yeah, it's a new cartridge, and new cartridges are always fun. At least to a point. But many come with more issues then they solve. Ammunition availability and cost are at the head of the list. Just ask anyone who bought a .45 GAP Glock. Or any of these short, fat wonder cartridges. (Remington Ultra Mags, or the Winchester WSSM's). Most have flopped commercially, making guns, ammo, and brass difficult to find. And expensive when you do.
It's advertised as, "More capacity than a 9 MM, More effective than a .380". Yes and no. If you're after both, simply carry any double stack 9 of your choice, with high performance self defense ammunition. There are plenty of double stack 9's out there, manufactured by everyone and their brother, that even small handed individuals can hold comfortably, and shoot accurately.
If you can control a 9 MM with high performance ammo, (which most anyone can with even the slightest bit of training and practice), this isn't going to offer you much of anything.
As was mentioned, I put this into the category of a solution looking for a problem. They're attempting to create a one that in reality doesn't exist, in order to sell it. You reach a saturation point with both pistol and rifle cartridges, where the market becomes fully soaked, and won't absorb any more.... Unless it's something really revolutionary. This isn't it.
Even the .40 S&W came out of the gate blazing, and sold very well. (Smith & Wesson made millions off it in the 90's). Then it slowly died off, as modern 9 MM self defense ammunition vastly improved. Which in turn somewhat diminished it's overall performance in comparison.
With that said, I congratulate Federal for taking the risk. I hope they get some type of reward from it all.