The only problem with it is that it is built somewhat lightly for a 357 magnum; however that was its main selling point and advantage.
A model 19 can "loosen-up" more quickly than an L or N frame revolver by shooting too many maximum (or over-maximum as they did regularly in days of yore) loads.
The model 19 (and the other K frame 357's) is vulnerable to the forcing cone splitting. This is only associated with firing full magnum loads with bullets of 125 grains or lighter.
You should closely inspect the gun for a evidence of a cracked forcing cone. Also check for a generally solid lock-up. I would also suggest carefully feeling along the cylinder chambers for the slightest signs of bulging, although that is rare. Other than that, check as you would any other S&W revolver.
If it passes inspection (which most will) you are set for a lifetime of pleasurable shooting from your Model 19. Do not shoot any full-powered 357 ammo loaded with 125 grain or lighter bullets. I would also suggest not shooting many full-powered magnum loads of any weight in it, although many folks do just that.
Another option to look at is an older dan wesson like a model 15. They're built a bit sturdier than model 19's and they don't have the ugly finish/billboard and awful trigger featured on Ruger guns.