I have a Advantage Arms .22 kit for my Glock 19, and I am happy with it. You must stick to the suggested ammo list, mine runs fine with Remington Golden Bullet and CCI Minimags. Federal is not known to work in most kits.
.22 lr ammo is going to be very hard to come by for the next 6 months, while you will have a much easier time finding .40. My 2 cents is unless you already have lots of CCI Minimags or Remington Golden bullets I would skip the conversion kit for now and use the money for .40 ammo.