I admire Bill T's loyalty, but Savage is right.
When the .40s&w was introduced, Glock was in such a rush to get one out the door that they just crammed it into a Glock 17 and said good enough. Very quickly it was clear that it wasn't good enough. Frames cracked right at the locking block and had to be redesigned with the new 3 pin frames. When the .357sig came out, same thing, frame rails were breaking and had to be redesigned.
.40 cal chambers have gone though changes to reduce the number of pressure excursions (kabooms), and they still have feeding issues anytime the .40 caliber Glock is shot without a locked, straight wrist behind the pistol, which is not always possible, especially in a defensive/law enforcement scenario.
Lets face it, the sights suck for anything other than close range daytime shooting, and those have been redisigned by Glock as well. Too many front sight were being bumped off the pistols. Now they use a metal front that screws on.
The list goes on....
Now the first generation Glock 9mm is a terrific design, and they are safe and reliable. Glock also did great work with the 10mm, but it's hardly perfect from the start.
I love my 3rd gen Glock 19, well proven, accurate, reliable, lightweight, rustproof, and now that I have good sights on it, perfect!
Just don't try to tell me they have been perfect from the get go.