I bought one a few years ago just for the heck of it and to go with some new ultralight backpacking gear. I have a Freedom Arms 454 Casull, a custom 500 Linebaugh and some other hand canons so I am no stranger to recoil.
The 340PD is pleasant for me to shoot with regular 38 loads. Hot 38+P loads produce some perceptible recoil but aren't terrible. Hot 357 loads, like Cor Bons, are truly brutal. Although the gun is surprisingly accurate with hot 357 loads on a 7 yd self defense target, it is extremely punishing to shoot. The only worse gun I've shot was a 4-barrel 357 derringer. Same type of snap but the barrels were off of the center axis so it torqued in your hand. Just awful.
I normally practice with 38s and 38+Ps and enjoy the gun. I think that good 38+Ps are probably adequate against most bad guys, if you hit them well. The only time I carry the 357 loads is while sleeping in black bear country, where I use jacketed rounds. Even for that application, some sturdy jacketed 38+Ps or handloads with hardcast bullets would likely do the trick.
If you are planning to carry a J frame for self defense, you can probably get an alloy frame suitable for 38+Ps for a lot less. However, if you have the money and want the 340PD, what the heck.
I put the Brownells spring kit in mine to reduce double action pull and had a gunsmith friend tweak it a little. After shooting mine, he bought one. The thing sits in your front pocket like it isn't even there.
DancesWithKnives