The really bad era for S&W was the Bangor Punta era. I reached legal age for buying firearms during that time, and so I developed an early aversion to S&W by seeing gaps where there should not be gaps, misaligned parts, and feeling the gritty actions. Not all Bangor Punta guns were bad; when I had to use personally-owned S&W revolvers as a young police officer, due to PD policy, I managed to find a really nice Model 581, to offset the horrendous 686 I had received sight unseen though a local vendor as part of a special deal for police cadets.
The LSI era was a breath of fresh air; all of a sudden, S&W revolvers were tightly fitted, and had decent to excellent actions. I bought a really sweet 3" Heavy-Barrel Model 60 during this time, and recently acquired an LSI-era Model 19-5, pre-owned, that appears unfired, that I consider one of the sweetest sixguns I have ever handled.
Things stayed quite good until the MIM trigger era. The contour of the MIM triggers does not work well for me; the "combat" width forged trigger is perfection for me, in DA fire, with K/L frames. An MIM trigger is hollow in the back, not suitable for being dressed-down to the feel I like. Therefore, my preference for sixguns built during the era of forged triggers. The Performance Center continued using forged triggers for at least a while after the standard models went MIM.
The keyhole is ugly, but the actual malfunctions attributed to the internal locks seems limited to certain lightweight models firing powerful cartridges. I am considering a certain J-frame purchase, which would be my first IL purchase. The MIM trigger is OK for me with J-sized guns.
Not all pre-Bangor Punta S&W revolvers were so great. I had an S-numbered (pre-N-frame designation) Model 58 with what felt like gravel in the action. I sold this one when I started divesting myself of N-frames, which I finally had to admit were too big for me to shoot well in DA. (I did, however, keep my ex-SAPD Model 58; we shared to many adventures for me to sell that one.)
To be clear, though I am better-known for what I have written on THR about my Rugers, I am still a fan of S&W, too. I am not a one-brand type of guy; an individual Colt, Ruger, or S&W weapon can make me feel all warm inside.