Tom we will continue to disagree because it is an effective round for what it is. It is light and small so you can carry a lot of rounds in a pistol. With the PS90 it has 50 rounds stock. The round doesn't overpenetrate and it does the job.
It's double the velocity of a 22 LR from a pistol so yes, I have carried the 5.7. I have never carried a 22LR or 22 mag for defense.
And no, you can't say the same thing about the 22LR and be honest about it because it's apples to oranges. The 22 LR is a slug puppy in a pistol....I don't want to be shot by one but there's a big loss in what little velocity it does start with. In fact, the 22 Magnum can only scoot maybe 1,300 FPS from a pistol barrel....which is still a lot less than a 5.7. Most, but now not all because of the PMR 30, of the 22 mag rounds are rifle powder slower burning rounds so there's quite a flash of unburned powder when you do shot one. Not so much with the 5.7.