Got one of the units you mentioned about a year ago for Glock 17 from the same folks. Accuracy is quite similar to 9mm barrel. I wish they would use sights that are more like what is on standard Glock slide. The ones on conversion kit are all black.
The biggest complaint I had / have with the thing is an excessive number of misfires. Seems like their instruction book said something to the effect of "common during 200 to 400 round break-in period", but mine was well beyond that and still having way too many - approx 30% of the time. I was prepared to ship it back to them and had called to do so when the girl suggsted I try Remington ammo. I found some and they wer somewhat better - maybe 1 out of 10.
I bought it to have for plinking, but primarily for use in starting out novices with .22 and then being able to transition with same gun to 9mm. The misfire problem mentioned about created such a goat orgy the first couple of times that I put it in student's hands, it was boxed up, cleaned up (again) and tossed in gun safe until I have more time to fool with it. In the meantime, I have been using other .22s that DO go bang every time the triggr is pulled ...
Sorry, I wish that I could give you a glowing report, but the above represents my experience to date. I think there are some other people who make .22 conversion kits too, but know not if for Glocks ... regards Greybeard