I have one .22 semiautomatic pistol, an AMT .22 Automag which I bought shortly after they first came out. It was my first handgun purchase.
It's sweet...6 inch barrel, 9 round magazine, slim, light, and accurate.
How accurate? I can hit a soda can at 100 yards with it from a bench rest. It might take me all 9 rounds in the magazine, but they'll ALL be impacting very close. Since this is open sight (no scope) from a 6 inch barrel, I call that darn good.
I've taken it frogging, squirrel hunting, and done tons of plinking with it.
It is by no means a quiet pistol, however. Easily the loudest out of the three I currently own (Colt 1991A1 .45 acp, Beretta 92FS 9mm), and an impressive 18 inch muzzel flash in low light conditions. But it's an absolute DREAM to shoot!
This has always been one of those guns that if you can't hit what you're aiming at, then the fault is the guy attached to the trigger finger.
I can't speak for the new .22 Automags, as they're made by a different company now. Presumably they're just as reliable and accurate as mine.
EDIT:
High Standard now makes these.
http://www.highstandard.com/index.php/weapons-a-products/weapons?id=111
If you're looking for reliability, accuracy, and power, this sure fits the bill. If you're looking for a cheap plinker/target shooter, then this ain't it. .22WMR is a lot more expensive than .22 LR.