So...from my viewpoint, it's a 100+ yd small varmint round when housed in a suitable rifle, but fills no discernible need in a handgun.
Other people have already pointed out that it does have self defense potential. I have a NAA Mini Master myself with two cylinders. I practice with the .22 LR cylinder. Also use it with that cylinder when I take it with me fishing. But I have chrono'ed that little gun with both cylinders and there is a substantial difference between .22 LR and .22 WMRF ammo. The four inch barrel helps compared to some of those much shorter barrels I'm sure. If I carry that little gun as a hideaway BUG, I put the .22 Magnum cylinder in it.