couldn't help but put my own 2 cents in. new guy here, sharing my own experience.
i have a 6 inch plain 686-6 that i bought last year. after shooting it a while, the rear sight had to be moved to the extreme right to get it to shoot point of aim at 25 yards. sent it back to smith, they rebarreled it, shoot great now, the only gun i have that i can use to shoot single holes at 25 yards.
after realizing i can't afford to shoot 38 all day long, i got a 617, also in 6 inch. shot over 30K and counting, no problems whatsoever.
wanted one more gun (always just one more), found a 686+ pro series at local gun show. traded for it, brought it home. after the excitement wore off, i noticed that the barrel wasn't only turned to left slightly, but it was also pointing to the left, off-axis

. sent it back to smith, they told me that it was within their tolerances. i couldn't stand it and got rid of it.
not having learned my lesson, i ordered a 686 ssr, sight unseen. this time, the barrel was turned still slightly to the left, and the result is that the front sight is higher on the right. barrel is not off-axis. took it to the range, it was pretty accurate, using whatever ammo wal-mart happened to have at the shelf. cleaned it and noticed that after cocking the hammer, the cylinder still had a bit of rotational play. checked by plain 686, no play on that one. i am debating whether or not to send it back to smith. customer service may have been good before, but with my 686+ pro series, they were a bit snippy.
so, to sum it up, the more discerning the customer, the better off you are inspecting the product closely before buying. if you can overlook small details as long at it goes bang, just go ahead and have your local shop order you one. older smiths may be an investment, newer ones are a little bit of a gamble. have to add, i don't know if the slab sided barrels accentuate small flaws in alignment more than the regular round ones.
and in case anyone was curious, i still want a performance center 627, but only if i can examine it first.