I have shot Smith's for 50 + years now...my first was a Model 28 with an "S" serial number. As far as the lock goes, it's an eyesore for sure, but in my use and that of close friends/family members, we've not had it malfunction whatsoever. Same with MIM parts.
Sleeved bbl's: I've bought two M-69's since they came out...really like the 4-1/4" bbl., making them light weight but with the option of carrying full house .44 magnums....as a rule, I load them with Skelton's 7.5 gr Unique with a good 140 gr. LSWC for 950 fps. At 38 oz., they're a dream to carry. The sleeved bbl's no longer bug me, tho the IL's are still an irritant. Smith claims the sleeved bbl's improve accuracy and they may be right or it might be better machine tools plus CNC improvements...I donno. I do know it's a fat tube, but without the weight and both guns are superbly accurate with Hornady's XTP's (200 & 240), as well as home cast LSWC's of wheel weight alloy. And BTW, I've shot both with full house loads...not fun...but accurate and an available option if you ever need them...
As to accuracy, the 4 Smiths I now own with the lock are at least as good as my pre-lock's going back to 1968 or so. I will say that the bluing/finishing has not kept up however. The modern guns just aren't the equal of even the Bangor Punta vintage Smiths.
Too, while I can't gripe about the single action trigger pulls on my IL revolvers, (they're about the same as before); the DA trigger pull weights have definitely increased markedly...and especially so in the "J" frame models.
Of the 4, IL equipped Smiths I've bought over the past decade, two have had to be returned to Smith for re-work. One, a .38 Spl, 637 for a locked up cylinder after less than 20 rounds. S&W did the work, on their dime, and I had the gun back in two weeks. The 2nd was a .22 lr M-63 for an uneven cylinder/forcing cone gap and lead spitting. That one took 3 months. In both cases, they did the work and ate the shipping both ways. They did not argue and gave me no grief...but both problems should have been caught in a GOOD QC program, IMHO.
Would I buy another...yep if they ever came out with something I'd really like...like a 631 "J" frame, 4" bbl. in .32 H&R, or a stainless M-16 without that $(&$)*Q$*!$ full length rib! But either, (or really any custom work and maybe even warranty work) may be out of the question until they set up operations in ? South Carolina is it? Long overdue, getting out of Massachusetts IMHO.
HTH's & Best Regards, Rod