Somehow this thread hasn't been all that surprising considering the topic.
Glock makes a rather simple, utilitarian and serviceable defensive pistol which can suit the needs of a number of folks.
As a Glock armorer I've certainly had the opportunity to replace a number of broken, damaged and worn parts in working LE Glock pistols. I can say the same for some other firearms for which I've been trained as an armorer. Hardly a surprise. Things can break. That's one of the reasons they make spare parts, you know.
As a matter of fact, this thread (and another one like it elsewhere) have reminded me that I need to put together a parts order for Glock. I haven't had the parts needed for some repairs for some Glocks that have been brought to my attention in recent months. My stock of parts slowly dwindled while my attention was occupied elsewhere, it seems.
Anyway, personally I tend to prefer Glocks chambered in 9mm.
I do own a G27, but only because it came to me for a price not likely to be repeated and I thought I'd give it a try. I decided to keep it, but it has been slightly less reliable when it comes to feeding issues than the G26. I think the brisk recoil of the .40 S&W cartridge requires more of the shooter than the 9mm cartridge, especially when fast-paced, difficult and complex courses-of-fire are involved, but I feel that way about other .40 guns, as well (and I own 5 pistols chambered in .40 S&W). I've run over 10,000 rounds through my G27 and have only experienced maybe over a dozen feeding issues (a couple of which were obviously ammo-related, so they can't really be attributed to the gun itself) and I can accept that for my needs.
I've handled and shot (and repaired) some Glock .45's, but the design just hasn't appealed to me enough when chambered in ,45 ACP for me to buy one of my own. I thought the G37 I handled and tried was interesting, but I don't need yet another cartridge in my personal collection.
Ditto the .357 Sig model/cartridge.
Matter of fact, ditto that for the G20, although when I tried one of the early ones imported in '90, using the standard Norma ammo of the time, I felt it was an interesting offering.
I suppose it would be fair to say that I've seen fewer problems in 9mm Glocks, and have heard of fewer problems reported in 9mm models by other LE armorers with whom I've spoken, than in other caliber offerings.
The tac-light issue affecting
some .40 guns (G22/23's) is real enough to the folks who have experienced it. I know of an agency where a friend worked, and for which I met their armorer, and their G22's were still experiencing erratic feeding issues when their folks attached lights to their guns. Last I heard they were going to try some brand new mag springs on their guns to see if that helped (and yet their guns were only 4-5 years old and should have come with the 11-coil mag springs when new).
I also listened to another armorer in my last Glock armorer class asking for some direction to get his own G23 reliably feeding when he attached a light. the advice he was given in the class? Try some different ammunition.
Maybe the new Gen4 guns will be another step along in hopefully resolving issues like these. Locking block, mag spring and mag follower revisions haven't seemed to have completely done the trick, yet.
I was sort of hoping that Glock would increase the slide mass of the .40 models at some point, since you can only go so far when increasing recoil spring rates, especially if you're going to use the same springs in 9mm guns. Unfortunately, that would also probably mean the slide profiles would be affected and new guns wouldn't fit in existing holsters for .40 models, which would probably be a marketing concern for both Glock and the holster makers. Dunno. Just idle speculation.
I'll be keeping my pair of subcompact Glocks.
For that matter, I'll also be keeping my pair of SW99's and my pair of M&P's.
The next plastic framed pistol I buy will be another M&P, though.
I've been to 6 armorer classes spread among the Glock, 99 and M&P pistol lines, and I don't really feel inclined to 'play favorites' among them. They all work well for their intended roles.
Bottom line?
Glock makes a fine and serviceable pistol.
It's just a handgun.
Just my thoughts.