This ought to be fun.....quick.
The predominant models people have had issues with are the ones that are chambered in .40S&W.
That said, many (if not most of us) has fired tens of thousands of rounds (100's of thousands collectively) through our .40S&W Glocks problem free. The other chamberings have not been associated with the KB nearly as often as the .40S&W....and the KB's that have been documented have been so over-discussed that people think its more of an issue than it actually is.
Can your gun malfunction....yes.
Will it....most likely, no.
I carry a G22 and have no fears whatsoever. I have never had an issue....not a single malfunction, FTF, FTE, or any other issue. The KB thing is way more hype than reality IMHO.
Any gun can malfunction....its a mechanical device, and things break.
The frequency with which they do, however, isnt enough to give me even a moment of pause.
The two most common supporting arguments for the .40's KB'ing are ......
Using unjacketed lead bullets....
&
Having an 'unsupported' chamber in these models.
Another less discussed issue is that in a Glock, the striker mechanism moves in the opposite direction of the chamber/round during firing which 'could' result in a slight movement in the slide toward the rear of a full battery position...thus extracting the round from being fully seated in the chamber and exposing hundredths of an inch of the rear of the casing...again, leaving that portion unsupported during ignition.
I was a late comer to Glocks....and I resisted them in favor of metal, proven, designs.
Eventually I tried one and came to realize that they are hugely popular for a reason...they are an awesome design and they shoot damn near perfected fresh out of the box. I am a pretty hard sell, and I'm a big fan of old-school steel...but i cant deny that after having had enough range time with the Glock...the myth of them being unreliable or even dangerous is overblown and frankly, ignorant.
Carry what you are comfortable with...but do some real research and get the facts....there are plenty of koolaid stands on both sides of this argument. Opinions prove nothing....get some facts and decide for yourself.