The responses so far are pretty much what I expected. Just to play devil's advocate and address a few of the issues...
For not being able to hit what you're aiming at; if you hit center mass, the fragments will all hit 7 inches from the center aiming point. It's kind of the point that it compensates for improper shot placement. For instance, it has a 14 inch diameter spread. If you're aiming for center mass and you pull a shot in any direction, one of the fragments will be pulled back toward your original aiming point. Basically, 7 inches of compensation in any direction.
So I guess, if you have good shot placement at center mass, you will have three fragments that hit not at your aiming point. If you have bad shot placement, you should have at least one fragment that hits close to your aiming point. If one or two of the fragments miss, he says they are supposed to vector back toward the center. I'm not sure how that would work exactly. If that did work like he said, then I'm sure that would further reduce any penetrating power they might have. But the point is to have a higher hit probability. In that aspect alone, yeah, I can see them increasing that.
The mindset of "I have no problem hitting my target" is great if you can actually do it. I do stationary shooting to different types of moving combat drills and I usually have no problem hitting my target either. However, I've never actually had to shoot at someone in a life or death situation. As much training as I can do, there is still no really good way to simulate that. I hope (and the training certainly helps) but I have no way to know what my shot placement would be like in that situation until it actually happens.
Tangling up, locking up your gun etc. are valid concerns as well but may never actually be a real issue. Lots of testing would have to be done before I'd be comfortable on that subject.
I think the biggest downfall would be the penetration power. They sell a "lethal" and a "stunner" version. The "stunner" version doesn't make much sense to me because I'm not a fan of any "less than lethal" round. But still, I don't see the "lethal" version being able to adequately penetrate.
Increasing hit probability, I will give them that. Being a viable stopping round, I don't think so. I'd still like to see penetration tests. But then again, they do recommend to only load one or two rounds and have the rest with your normal carry load. So, the point is to at least get the first one or two rounds on target.