Having been upset with the way my Walther P22 turned out, I wanted to try something different in a .22 pistol. I like the idea of training for cheaper since ammo prices have gotten out of control recently. Since trigger control and sight picture are the real keys to good shooting, this is a great way to obtain or maintain some degree of skill and familiarity with the Glock pistol.
They claim on their website that "You will have paid for your ADVANTAGE ARMS, INC. conversion kit after shooting 1000 rounds of .22LR."
I guess it depends on how much you are paying for ammo... Nevertheless, they make a point if you shoot a lot and are looking for a cheaper alternative.
I got a conversion to work with my Glock 27 and it turned out well for the most part. They are available for several models of the Glock as well as the 1911, two of the most common and well known pistol designs out there. The Advantage Arms .22 Conversions have been around for a while and they go for about $250 or so for the one I got.
It didn't like bulk Federal .22LR ammo but it did fine with the Remington bulk stuff I have tried in it, which by the way is the same ammo they recommend for plinking with. Although the accuracy is not excellent with it. They say to try "CCI MiniMags or Federal Automatch" for better accuracy, which I never tried, since I have had a hard time finding anything other than Bulk ammo lately.
Overall, I was impressed with it. The upside is that I get to train with a pistol that feels just like a Glock but in .22 and that it will take at least some form of bulk ammo. The downside is that for about the price they charge you can get a complete pistol in many cases, and it can have a hard time with some bulk ammo, outside of Remington.