I've heard the term "write once, test everywhere!" But, since testing is actually a good thing, I think the spirit of the quote is "write once, fix glitches everywhere"

I am extremely hopeful about React. Even though I know Objective C and have apps in the app store, I'd use a cross-platform toolkit if I could get Android and Windows for free (or minimal effort). In my past experience it didn't really play out that way, but I am ever hopeful that this time it will really work.