I have a tactical solutions conversion and I love it!! I've owned a ceiner and it was ok but I like this one the most. It uses real glock sights also so you can train with what you use. Mine has a threaded barrel so I can shot with my suppressor also. I'm a firm believer in "beware the man with one gun, he knows how to use it!" I have a glock 17 and the conversion with a dedicated lower. Mine is very accurate also it's always riding with me in my gator and has dispatched plenty of critters too. The only negative is finding 22 but boost at keeps improving. I know they are pricey but I know I'm getting my money's worth. I actually found a good deal on a 17 and since the upper sat around I sold it on eBay for $325 to help pay for conversion and kept the mags.
I have an Advantage Arms G19 kit; works great and is one of the best gun things I have spent money on. Rem Gold Bullets inexplicably run like a top, but Mini-Mag and AR Tactical are very reliable after the first hundred or so rounds. After a few hundred through the kit, CCI SV is 100% but will start to choke in a dirty gun before high velocity ammo will. Thunderbolts, AutoMatch and Fed Bulk are no bueno, though.
GREAT for introducing novice shooters and wives/kids to handguns and obviously for plinking or training. I have no problem consistently hitting a 8" steel plate at 30 yards with mine.
Their prices have come down somewhat since I got my kit, and there are more/better 22LR pistols on the market today than there were a few years ago.
I've kicked the idea around of selling my AA kit and getting a M&P22 Compact, but I kinda like being able to train with my carry pistol with the only difference being weight of the slide.
I have an Advangage Arms .22 Conversion kit. If its clean and the ammo is good, it works well. It can be tempermental and picky about ammo, though. Overall, I'm glad I bought it.