Several of our members have them and post pics from time to time. Opinions vary, as you would expect. The one I had "on loan" years ago was an 8-inch gun and it did seem to be a bit less accurate with .22LR, but truth be told, I shot it a lot more with magnums and wasn't scientific at all with the LRs. I believe that particular gun opened up about 1/2" at 25-yards with the LRs. I could not negotiate a satisfactory price on the gun and, being cheap, ended up with just a plain old (single cylinder) Model 48.

You don't see a lot of them, but I wouldn't call them rare. Wouldn't be able to guess at value without more info on your gun, and even then, it is a niche market and not everyone will pay top dollar for the gun.

I have always thought of them as about the same as having the extra .22LR cylinder for the Jet. Darned nice to have, but mainly useful in the original caliber. I rarely shoot .22LRs in a Model 53, and probably would do the same with the dual-cylinder 48. But as I said, darned nice to have!