I spent just shy of 20 years as a firearms instructor working with folks carrying issued S&W traditional double action '3rd gen' pistols.
I spent a number of years of that time having the opportunity to attend S&W armorer classes. I was responsible for helping maintain the agency's inventory of several hundred S&W pistols, as well as a respectable number of personally owned S&W pistols used as authorized off-duty weapons.
While I was not an 'enthusiast' of S&W pistols prior to the introduction of the '3rd gen' models, I developed quite a bit of respect for them during my time spent carrying various issued models and working as a firearms instructor & certified armorer.
I own a fair number of them and have great respect for their reliability and durability.
If basic cleaning & lubrication user maintenance is done, including replacing the recoil & magazine springs either every 5 years of use or every 5,000 rounds fired, they can offer good service. Naturally, it's recommended that LE armorers set up some periodic inspection schedule to check LE guns, especially since LE guns can be subjected to a lot of conditions which can border on abuse.
Yes, there are a couple of parts which usually require fitting when replacing them for repair purpose, namely extractor & sear release lever. Fitting an extractor does require a couple of specific tools, as well, such as a Go/No-Go bar gauge and a force dial gauge. Obviously not something recommended for the untrained owner/user to attempt.
A broken trigger play spring may result in some folks feeling a bit of a sloppy single action trigger, but a number of folks have never noticed when the springs have broken under normal training/practice conditions. FWIW, I had one break in a well-used early production 6906 which had seen more than 10,000 rounds fired through it ... (just by me, and it had been previously issued before I got it) ... at some point during a couple of range sessions over the course of which I fired more than 800+ rounds, and I never noticed it until I was inspecting& cleaning the gun afterward. The replacement is pretty simple (it's just staked on the drawbar with a soft rivet), but it requires knowledge of detailed disassembly of the frame.
The occasional replacement barrel may require some minor fitting (barrel tab area), and even more uncommonly the rare drawbar may require some filing in the radius behind the drawbar head.
These are fairly simple repairs for a trained armorer, the factory or a licensed gunsmith familiar with S&W pistols.
I continue to carry and use S&W 3rd gen pistols now that I'm retired and I consider them to be generally overlooked and under appreciated as good, solid & reliable defensive pistols.
Just my thoughts.