I've shot 44mags, 454 Casull, and a couple of Smith's new big bores and I would shoot them again.
One gun that I'm hesitant to shoot again is the S&W Scandium Snub Nose. I believe it was the 340? My friend who is a Chicago Police Officer uses one as an ankle gun but usually loads .38 +P rounds. At our last range outing, he decided to load it up with some .357 rounds and hand it over to me.
I once read a review where the shooter described the flame out of the front being similar to an orangutan jumping out of the barrel. I have to admit that that was a pretty accurate description. We were shooting indoors and this gun roars! The recoil made my had physically sore after 3 cylinders and I quit.
I'm sure in a defensive scenario, adrenaline would kick in so you really wouldn't feel or hear much of it but if I were given the chance to step up to the line and shoot it again, I think I would pass.
I shot my 642 Powerport right after shooting his and mine felt like a .22 with standard .38 rounds.
If anyone is curious, the porting up front of the 642 Powerport has yet to spit up hot gasses (even when shot from close retention) or has caused any excess noise like some claimed it would because it was ported. It's the only gun I have with a lock but it doesn't bother me and I love it. Probably one of my favorite guns.