My first 720 had been abused. Someone apparently dry fired it a lot, slammed the cylinder shut, didn't clean it, etc. It had to have all of the gunk cleaned out of its insides to function, the crane needed to be adjusted, and the hammer nose broke after only a few hundred rounds. A S&W Model 10 hammer nose will fit and function if you file it a little bit. It's been fine for 1,000 rounds or so since. It wouldn't be my first choice for carry given its checkered past, but it's a great gun to shoot.
My hammerless one has a dreadful trigger. Apparently the original owner or owners felt the same, because it doesn't appear to have ever been fired much. It's given me no problems in the 150 or so rounds I've shot it.