Over the past nearly 15 years of competitive shooting I have had or seen a fair number of S&W revolvers crash and burn (stop working) and I have to say I have never seen one fail due to a cylinder release failing in the open position. I have seen it fall off but never fail in such a way as to leaving the revolver unlocked. Maybe it can happen but I have not seen it.
My reason really has nothing to do with a potential mechanical failure and more to do with ergonomics and reloading quickly. That rearward motion of a Colt cylinder release is simply not as ergonomic and efficient of a motion if your trying to reload a revolver quickly, such as is common in USPSA, IDPA, and the fiction Self-Defense scenarios rolling around in my well deluded head. These fantasies prompted the somewhat satirical comment that a Colt will get you killed on the streets.
As I alluded to in the second half of my earlier post there is a reason S&W dominates those sports and the cylinder release is very much part of that domination. The push forward motion of a S&W revolver is simply faster and more efficient whether you're a strong hand or weak-hand re-loader, especially if you're feeding your revolver moonclips. Since I started shooting USPSA in 2005 I have seen lot of S&W revolver in competition, a few Rugers, a Webley Mark VI and even a Dan Wesson but I have never seen Colt. If the Colt was faster the competitive shooters would be using it (despite the crazy Colt prices) and they are not.
-rambling