I agree DHart. Well said. I am more comfortable with a 9 mm, but would be fine with a .40 if that's what I had to carry. I am confident with time and practice my speed and accuracy would not suffer much. I would not spend a second worrying about premature failure of any components, including the polymer frame.
K_Mac: thank you.
Regarding you or anyone (possibly) trying out forty... if someone new to .40S&W were to ask me, I would strongly encourage seeking out pistols like the M&P40, Sig P320 40, HK VP40, Walther PPQ 40, or Browning HiPower 40. Load with run of the mill 180 gr FMJ from MagTech, American Eagle, Win WHite Box, S&B, or PMC. Then have at it!
First thing you'll notice is that the recoil is noticeably milder than .45auto, barely much more than 9mm +P, though the recoil impulse has a similar soft "push" to a 230 gr. .45auto round. And you'll notice that the pistol returns to target significantly quicker. Nice! And soft-shooting - not "snappy". Not the least bit uncomfortable - quite fun, in fact. .40S&W is supremely "in its element" when fired from any of these great pistols.
The triggers on those pistols are quite good, especially after they've had a few hundred rounds through them. More importantly, the grips on those pistols are so well designed that the guns just feel fantastic in your hand. The accuracy and reliability are fully there, as well. And, importantly, you'll also notice that the mag capacity is right up there.
Then load in some premium defense ammo, such as Federal 180 gr HST, 180 gr. Ranger, or 180 gr. Gold Dot.
Surprisingly, the recoil with that is hardly any more than with the basic target ammo you were just shooting with.
Then, do some homework on how well 180 gr HST performs as a defense load. It performs exceptionally well! And that bullet weight is known to bust through bones, without deflecting, and will continue on with very deep penetration and wide expansion. This is especially important if your target is not standing perfectly aligned toward you, straight at you, with his arms down to the side - but rather your adversary has arms outstretched in front toward you, or is turned somewhat to the side toward you... then you'll really appreciate the greater bone busting ability of heavier calibers with heavier bullet weight.
.40S&W, when the various loads are understood and when enjoyed with a great pistol that is expecially well suited to it, is an exceptionally smart choice in a defense pistol. It combines major amounts of the best of .45auto and 9mm all together. Potent power, easy-shootability, and high capacity. There is a lot to love about that blend of benefits.
And, though Glock forty caliber pistols are every bit as reliable and accurate as the other pistols that I mentioned, Glock forties do not feel as soft-shooting as those other models. Having owned and been shooting almost a dozen different .40S&W pistols over the last ten years or so, including three Glock forties, I would unhesitatingly steer any new .40S&W shooter away from Glock and toward any of the other models I mentioned above. The experience of shooting a Glock 23, for example, particularly with a 165 gr. Defense load, is nothing at all like the experience of shooting 180 gr loads in any of the aforementioned pistols. Like night and day, in my opinion. Ultimately, I've converted my remaining G22 Gen 4 and G23 Gen 4 to 9mm and now I can enjoy them again. But my favorite caliber remains .40S&W, firing an M&P40, P320 40, STI Edge 40, or Browning HiPower 40. I love .45auto, as well. For me, 9mm is "okay", and best reserved for my PM9 and P938. I enjoy shooting 9mm, but if I knew I needed to defend myself with a pistol, my top choices would be my M&P40 with 16-rounds of 180 gr HST on board, P320 40 with 15-rounds of the same, and my STI Edge with 18-rounds of the same.
Finally, if you somehow find yourself requiring a pocket-sized pistol - stick with 9mm. I know the temptation to acquire a pocket sized pistol with a 3" barrel in .45auto or .40S&W and while it is "do-able" I personally think that 9mm is a much more effective caliber than the larger calibers, in very small pistols. In my view, .40S&W is best served from compact, mid-size, and larger pistols. And .45auto is best served from mid-size and full-size pistols.