According to a couple of local Dealers, Glock hates aftermarket barrels. They may yet put their money where their hate is and build 106mm factory 9mm, .357 SIG and .40 S&W barrels. This has, however, been an an awfully long time coming.
I have a Glock 19 Bar-Sto barrel which needs the feed ramp polished and softened, it has FTF issues with certain ammo. The ramp is visibly steeper than a factory one, and with the tighter chamber too, disaster. $300 plus barrel... Supposedly at the peak of aftermarket quality. I have never, in thousands of factory rounds through my various Glock factory barrels, had a FTF or FTE.
Lone Wolf has finish problems, though their barrels seem OK otherwise. Storm Lake and IGB seem fine, and the new EFK barrels in the Glock 43 are excellent.
If threaded factory barrels offend you, most gunsmiths will recrown a Glock 19 barrel at 105.5 mm or so for around $75. That still leaves a small "step", barely visible and not offensive to me, and if done right, slightly improved accuracy. A good craftsman will take his time and do it in 10 minutes or so, instead of the under-10-second job lovingly done by CNC gear at the factory. It seems to me that the barrels are crowned and then threaded, and I imagine that the threading process causes minor deformations of the barrel crown. Probably all my imagination, but my pistols seem to shoot better when they've had their threaded barrels re-crowned.