I wonder what the specs on the strength of this 'new stainless steel' are. I highly doubt that Apple is now pioneering new innovations in the realm of metallurgy "just to bring you a better iPhone," though their marketing would probably have you believe otherwise.
"Strength" of a metal is always a tweaked compromise of hardness and toughness. It could be that their steel is formulated specially for the particular structure of the iPhone 4. This wouldn't be a new pioneering branch of metallurgy, though it could be spun like that by marketdroids.
Agreed, drop a little more carbon into the steel and you've got your own new stainless steel that for all intensive purposes is probably identical to 3,000 types of steel already on the market by different producers globally.
Steel is steel, they probably researched the steel that works best as an antenna whilst not compromising the physical strength of the unit (for instance, you don't want the metal case to be the thing most likely to shatter on the device).
