I'm still pretty ambivalent about it. I don't think it's a bad cartridge, but at the same time I don't think it's head and shoulders above the other popular "service" handgun cartridges either. Honestly, about the only interest I'd have in buying a gun in .40 S&W is to have another caliber choice when ammo gets scarce as it did in 2008/2009 and 2012/2013. Beyond that, I already own semi-autos in 9mm, 10mm, and .45 ACP as well as revolvers in .38 Special, .357 Magnum, .41 Magnum, .44 Special, and .44 Magnum and I just don't see a .40 being able to do anything that I couldn't accomplish with at least one of those other calibers.
As to the notion of the 9mm improving so much, I think one needs to understand that the 9mm needed more improving to begin with. To understand this, you really need to look back more than 10 years, more like 20-25 years when the .40 first debuted. Back then, bullets which we consider very dated like Winchester Silvertip and Federal Hydra-Shok were the latest and greatest. The 9mm, at that time, basically offered two choices: a light, fast 115gr bullet which expanded well, often to the point of fragmentation, but didn't penetrate very deeply or a heavier, slower 147gr bullet which penetrated quite well but didn't expand reliably.
The .40 S&W and .45 ACP, on the other hand offered large enough hollowpoint cavities to expand at lower velocities than the 9mm and, even with lighter, faster bullets, could still sling a heavy enough bullet to penetrate reasonably well even if they fragmented moderately. Revolver rounds like .38 Special and .357 Magnum could also use bullets of different construction, like dead-soft swaged lead or semi-jacketed hollowpoints which wouldn't reliably feed in a semi-automatic and Magnums simply had enough sheer horsepower to make bullets which would act like FMJ at 9mm velocities expand.
You must also remember that, even after better bullets like Gold Dots or Black Talon/SXT/Ranger came to be, their availability was often limited. The Black Talon in particular was only offered to the non-LE market for a short time before Winchester restricted it to the Ranger line due to bad PR. Also, until the late 90's the internet was in its infancy and mail-order/online ammo sales were not what they are today. Simply put, many people were restricted in their choice of ammo to what they could find in stock locally and, if all that was available was older JHP designs, the .38 Special, .357 Magnum, .40 S&W, and .45 ACP could make better use of them.
Today, however, modern JHP designs have allowed the lighter, faster 9mm loadings to hold together and penetrate better and the heavier, slower ones to expand reliably. While those same improvements have also been applied to the other service cartridges, the difference isn't as noticeable because they weren't all that bad to begin with. Also, most modern JHP bullets, regardless of caliber, are all designed to do pretty much the same thing: expand to 1.5-2x their original diameter and penetrate 12-16". While modern .40 S&W bullets can certainly do this, many of the older ones could too so the difference between the .40 and 9mm has shrunk.
As to the notion of the 9mm improving so much, I think one needs to understand that the 9mm needed more improving to begin with. To understand this, you really need to look back more than 10 years, more like 20-25 years when the .40 first debuted. Back then, bullets which we consider very dated like Winchester Silvertip and Federal Hydra-Shok were the latest and greatest. The 9mm, at that time, basically offered two choices: a light, fast 115gr bullet which expanded well, often to the point of fragmentation, but didn't penetrate very deeply or a heavier, slower 147gr bullet which penetrated quite well but didn't expand reliably.
The .40 S&W and .45 ACP, on the other hand offered large enough hollowpoint cavities to expand at lower velocities than the 9mm and, even with lighter, faster bullets, could still sling a heavy enough bullet to penetrate reasonably well even if they fragmented moderately. Revolver rounds like .38 Special and .357 Magnum could also use bullets of different construction, like dead-soft swaged lead or semi-jacketed hollowpoints which wouldn't reliably feed in a semi-automatic and Magnums simply had enough sheer horsepower to make bullets which would act like FMJ at 9mm velocities expand.
You must also remember that, even after better bullets like Gold Dots or Black Talon/SXT/Ranger came to be, their availability was often limited. The Black Talon in particular was only offered to the non-LE market for a short time before Winchester restricted it to the Ranger line due to bad PR. Also, until the late 90's the internet was in its infancy and mail-order/online ammo sales were not what they are today. Simply put, many people were restricted in their choice of ammo to what they could find in stock locally and, if all that was available was older JHP designs, the .38 Special, .357 Magnum, .40 S&W, and .45 ACP could make better use of them.
Today, however, modern JHP designs have allowed the lighter, faster 9mm loadings to hold together and penetrate better and the heavier, slower ones to expand reliably. While those same improvements have also been applied to the other service cartridges, the difference isn't as noticeable because they weren't all that bad to begin with. Also, most modern JHP bullets, regardless of caliber, are all designed to do pretty much the same thing: expand to 1.5-2x their original diameter and penetrate 12-16". While modern .40 S&W bullets can certainly do this, many of the older ones could too so the difference between the .40 and 9mm has shrunk.
