I have a 340PD, and I like it. What Joni Lynn says about selecting bullet weights is right on target, IMHO. The gun is not that bad with 125s, but full-charge .357s with 158 gr bullets are beyond my ability to tolerate. I generally keep my gun loaded with Winchester Silvertips. I know, they are "old fashioned"
but they are about as much as I can handle.
I think if I had it to do over again, I would prefer the M&P model. The SS cylinder would be a good thing. But as it is, my 340PD hasn't caused any trouble. I intend to disable the IL some day, but until now, even that has been trouble-free. Never had a key in it.
It is amazing to me a gun like this thing stays together and is able to work as well as it does!