There are a lot of discussions about this topic on this site. You are about to quickly learn that everyone has strong opinions on the matter.
As for me, I've purchased 3 Smiths with locks in the last year, and I don't give it a second thought. True, the lock is an unnecessary mechanical part that can fail just like any other mechanical part, however the chances are very very very slim. Who knows what the statistical probability is that one might have a critical lock failure, however I would venture to say that you would be better off worrying about getting hit by a car, or maybe even getting struck by lightning during your gun fight