Gun writer Michael Bane reports a failure of the internal lock on his Model 329PD. It will be interesting to see how Smith & Wesson attempts to respond to this.
The internal lock on handguns is something that will probably not go away for the foreseeable future. They are standard on Taurus, HK, Bersa, Springfield Armory 1911-pattern guns, some Rugers, S&W revolvers, and optional on Glocks and some S&W autoloaders. I'm fairly agnostic on the whole concept; from a philosophical standpoint it's no better or worse than a separate locking device like the cable or trigger locks that some folks use religiously to store guns and others ignore. My main objections are aesthetic and mechanical.
The best lock would be one that is invisible, or nearly so, on the exterior of the firearm, especially on guns that are frequently bought for their aesthetics, such as revolvers or 1911-type guns and can be removed and replaced with no permanent alterations to the firearm. Probably the winner in this category is Springfield's ILS, which is contained entirely within the mainspring housing of the pistol, and can be swapped out with a standard 1911 MSH if one is so inclined. While some have complained that Springfield should make it optional, from a business standpoint it's probably cheaper to have one part and one box label and let the customer decide if they wish to leave it on the gun.
The one that has drawn the most fire is Smith & Wesson's revolver lock, and it's because of both aesthetic and mechanical reasons. First, S&W revolver buyers are generally a conservative lot, and aesthetics enter into their purchasing decisions; many of them will defend their loyalty to S&W revolvers over their Ruger counterparts on looks alone. Smith's lock design puts a keyhole right on the side of the revolver's frame, just above the cylinder release. While not particularly noticeable on a blued gun, it sticks out like a sore thumb on a stainless piece, and is also fairly disharmonius on the newer lines of "retro" revolvers S&W has been hawking.
Worse, from a mechanical standpoint, the lock requires internal bits to rotate towards the rear of the gun to engage the lock. On the new flyweight Scandium magnums, several bazillion "Gees" of energy are jumping the gun to the rear under recoil and reports have come in, Mr. Bane's being merely the latest, of that force being sufficient to partially engage the lock, thereby tying up the gun in a manner that requires tools to unjam. I myself have seen it happen to a customer's Model 357PD, a sub-2-pound flyweight shooting middling-heavy .41 Magnum ammunition.
I personally own two Smiths with the lock, a 432PD and a Model 21 Thunder Ranch, neither of which I'm particularly worried about as neither generates the sharp recoil that seems to cause this, and it never happened on my long-gone Model 325PD as apparently .45ACP in a 21.5 oz. package doesn't have the wheaties, either. I'd be leery, though, of the Scandium .357 J-frames and the .41 and .44 Magnum N-frames with the lock. Not good, as the former is designed as goblin-repellent and the latter two are marketed for self-defense in bear country. Were I to, for some unfathomable reason, wind up with one, I'd probably eighty-six the lock. Some things just don't need built-in failure modes, especially when a grizzly is gnawing on your ankle...