I've had two, both were 686's. First one was a LH 2.5" I bought new. It had a dead cylinder, by this I mean that every so often that one cylinder would not fire. You'd never know when, but it was constant enough to make me aware and thankful when a full 6 shots worked - kind of like a scratch on a record you like - you get used to the scratch spot.
Traded it off with full disclosure to a gunsmith.
The other was a 4" 686-2 that shot LOW. No matter what I did, it shot low with my ammo. I even replaced the rear sight blade with S&W's tallest blade and it was almost acceptable, but when a 4" 586-1 appeared at the local candy store, I sold it and bought the better 586. The finish of the 686 was best described as rough. Tool marks, sharp edges, unfinished rough edges on the forcing come - not the best foot forward IMO.
Add to this, the barrel was clocked when I got it and I sent it to S&W on my dime for that and to get it to shoot to POA. S&W did neither correctly and it still shot low and had a clocked (just not as bad) barrel.
It got sold.
The 586 shoots perfectly with my ammo using the 6 O'Clock hold I favor. Feels better when shooting too, but I can't pin down why that would be. I use the same Hogue grip I swapped over from the 686.