Got one for my wife a couple years ago and she loves it. To address your concerns:
Accuracy - It's surprisingly accurate for the short 3.something" barrel and since it comes with lots of adjustability (front sight, rear sight, grip backs) you can customize it to shoot and fit just right.
Size - For pocket carry, it may be a little big depending on your pocket size. It'll fit easily in a cargo pants pocket and you'd forget you're wearing it in an IWB holster.
Reliability - Ours is picky with ammo. It usually works well with Remington bulk from Wally, but out of the 550 there's usually a handful that give problems. My advise if you wanted to use it for SD and not just plinking would be to load it with Stingers or MiniMags which have always worked.
If you want to read more from "experts" go to rimfirecentral.com where they have a dedicated forum on the P22 along with any tweaks to increase reliability and performance.
Let me suggest another little 22lr that I have and have used for pocket carry. A Bersa Thunder22 or Firestorm 22. They are basically the same gun as the Bersa Thunder 380 except chambered in 22lr. I love mine. It's of similar size to the P22 so it's not any smaller, but with a proper pocket holster it works. My favorite thing over the P22 is that the Bersa breaks down and goes back together so much easier and it also just feels good in my hand.
This is a Firestorm 22. The main differences you'll see are rubber finger grips and a rounded trigger guard otherwise they are exactly the same.