I have an Advantage arms kit, and as previously said it is a little sensitive to ammo. The cheaper stuff tends to be less then 40 gr bullet weight which is the recommended weight for the kit to work correctly. I've found that it likes any of the stuff that is on the martket currently for the .22 AR convsersions as well. Also the gun is very sensitive to limp wristing, and if your lower has been tuned by polishing the connector or is really well used the kit will not engage the connector and go G18 on you. Lots of folks like to complain about the weight beign to light for training, it is fairly light loaded even compared to an empty stock gun. This can be corrected somewhat by using a Seattle Slug in the grip to get the weight up a little to make the draw's more similar, but you get punished if your grip isn't good with feeding issues.
It's a great tool for learning trigger control and site acquistion, get the LE kit and you can do like I have and put on the same sites you run on your stock weapon. It's better then dry firing, especially with steel targets because you get the instant gratification hit feedback for a job well done.
I've got a kit for the fullsize frames, one for the subcompact frames and one that runs on my G30 frame. All run good, but the smaller ones are a little more prone to feed issues. I shot more then a few steel matches with the G17/22 kit on the gun and it hasn't let me down yet.
I've also tried the tactical solutions kit. It was an early one and had some issues, but shows alot of promise. The wieght is more close to form and the mags supposedly will be hi cap, the kit I tried was 10 round only.
