First off, $800 is IMHO way too high for a used 686 lock or not. I can buy a brand new 686 locally for $700-750 and unless a gun is a particularly rare or collectable variation (which a 686 is not) I refuse to pay a higher price for a used gun than a new one.
Secondly, the lock makes no difference in the actual functioning of the gun. I have personally owned S&W revolvers made in the 1970's (M28-2 and M36 no-dash), 1980's (M66-2), and 2000's (M21-4 and 629-6) and I can't tell a bit of difference between them in terms of accuracy, reliability, or smoothness of the action.
Inevitably, someone is liable to come along and tell you that the lock will engage itself and get you killed when you need to use the gun; such is not the case. The actual number of S&W revolvers that can be verified to have malfunctioned because of the lock is so small that it's statistically insignificant. Of the few revolvers that have had problems, the problems typically manifest themselves very early on and do not repeat themselves once the gun has taken a trip back to Springfield. The design of the lock is such that the recoil arc forces the lock "flag" down and out of engagement leading me to beleive that the few verifiable cases of lock-induced malfunction are attributable to QC rather than design issues.
When you get right down to it, the vast majority of people who dislike the lock feel the way they do because of asthetics, traditionalism, or politics (the lock was introduced shortly after the infamous "Agreement of 2000" between the former owners of S&W and the Clinton Administration). If someone dislikes lock-equipped guns for these reasons, that's fine; a person may like or dislike whatever he or she sees fit for whatever reason he or she sees fit. Unfortunately, some of these people have stooped to using childish invectives like "Safety Wesson", "Smith & Clinton", or "Wind-up Guns". Even worse, some of these people attempt to blow the very few documented lock-incuced malfunctions completely out of proportion through clever uses of internet fora in order to justify their own preferences (that this "tempest in a teapot" drives the price of pre-lock guns up is also a convenient coincidence methinks).
Basically, if you don't like a lock-equipped gun because of looks, traditionalism, or politics then there is no reason to buy one. There are indeed a great many pre-lock 686's out there (though they may be selling for a premium now). However, if you are primarily interested in the function of the revolver, then I see no reason to pay a premium for a pre-lock gun when a post-lock example will do the exact same thing.