Never had a stainless firearm.  How strong is stainless.  I have a few standard carbon steel blued Walthers.   What are the thoughts ?

I guess it all depends on how you define strong or what you're comparing it to?

It's certainly strong enough to more than contain a .380 or .32 round (by which I mean I've never heard of a PPK kaboom like a Glock kaboom)

Firearms grade stainless is PLENTY strong enough.
Much depends on how it's heat treated, and gun makers usually heat treat various components according to the use the parts is for and the cartridge it's made to use.

If S&W can make a stainless steel .500 caliber revolver a .380 is no problem.

A stainless Walther PP series pistol will last a lifetime.

As others have said, it's subjective, but generally it's less "strong" than carbon steel (but, again, depends on grade of steel, hardening, etc.).  Unless you plan on running 100,000 rounds through it, which would be masochistic with a PPK, I doubt you, your kids, and your grandkids will likely ever see the difference.  It's definitely stronger than any aluminum alloy used for lightweight guns - before someone mentions it, I know there are aluminum alloys that come close to the strength of some steel, but they're ungodly expensive and used in specialized applications, e.g., not the frame of a mass-produced firearm.