I don't know if they still do it, but the P22s used to have a letter code that tell you how far into production you specific handgun was. I believe it started with AA. Somewhere about AG is where the serious problems with the P22 started to fade away. Before them, the guns had many serious problems, including a malfunctioning safety, parts breakage, FTFs, FTEs etc.
Early P22s earned a truly horrible reputation. What is unfortunate for Walther is that layer, and current generation P22s are only regarded as OKAY. With the current crop of semi-auto 22s, okay just doesn't cut it.