I have a Ruger convertible with the .22 magnum cylinder. When it was new in '73, I ran a few rounds through the magnum cylinder to see what it was like. The ballistics on the little round are interesting, although perhaps more so in the rifle, but I haven't shot that cylinder since.
Performance isn't what I object to. For a small cartridge, I imagine it would do well. The problem is that with cast bullets I can shoot 45 Colt, 44 Special, 44 WCF, 38 WCF, 32 WCF, and .38 Special cheaper. If I can track down the fired case, 45 ACP is cheaper as well.
If you can afford to pay that much every time you decide to pot something, I think .22 magnum would be an interesting cartridge. I find myself especially drawn to the idea of the NAA with the swing out cylinder, a gun intended not to be shot a lot but strictly last ditch.