There have been documented cases where the lock engaged and effectively made the revolver useless except to throw it like a rock.
Go to
http://smith-wessonforum.com and write in lock in the search area and you will find all you want to know about the lock and probably more.
Personally, if the revolver has the lock and is to be used for defense then I would not feel comfortable knowing it might not work when needed. If the revolver is for the range or plinking then it would be fine.
Your LIFE -- your CHOICE !!!!!!!!!