I have the AA conversion on a Glock 20. As long as I stick to their list of recommended ammo, I can say I have never had a failure. Very well put together and a great way to practice with the 20. With the cost of 10mm ammo, this has more then paid for itself. There are a lot of good articles on the AA. I have no experience with any other .22 conversion. Good luck.
I have an AA kit for my 23 and usually have a couple of FTFs every several magazines or so. They aren't perfect, but the cost savings are so immense that it is still worth it IMHO. However, I also second the fact that you need to stick with the recommended ammo. CCI Mini Mags are the best, but I've had overall good luck with the Remington Gold Box from Walmart. They are half the price of the Mini Mags too, I can get them at my local WM right now for $18.50 for 550 rds., the CCI Mini Mags are also at WM for $6.50/100 rds.
I have the AAkit for my G26. I had some problems with it at first but a trip back to the factory for warranty work, change to update magazines and it functions beautifully. I found the CCI minimags that are the 40 gr round nosedrounds work the best. the 36 gr hollow point, not so good. Be carefull which ones you pick up. I really like the AA kit.
I recently bought a used AA kit for my 2nd gen G19. Using the included magazine, I was experiencing 4-5 FTF's per mag. I bought 3 new mags for it and the problem seems to have mostly gone away. The 3 new magazines are noticeably different than the magazine that was included, so they must have done a redesign along the way.
I have an AA kit for my G26 and I only shoot Remington Gold rounds through it. I occasionally have a few FTF or FTE but not often. It only comes with one mag so I bought 3 more mags, makes shooting it enjoyable. Shooting the AA conversion on my G26 has helped me with my trigger pull on my G26 and its MUCH cheaper. Of course you can always just run dry fire drills at home but I like the gun to go bang when I pull the trigger.
Lately these AA kits have been hard to find...have to just keep checking the various websites that sell them. They also are a bit pricey, seen them running $250-$325.