Good article! Funny thing is, I do pronounce it yunz, yet always spelled it yinz...even in the 1960's, when I actually learned to spell! And like author Richard Peterson, I too lost my Pittsburgh accent (when I moved to the Midwest), and eventually stopped using that word in elementary school! (For folks who know how unique an accent is Pittsburghese, you'll appreciate this: My Illinois classmates thought my accent meant I was from England!!!)
By the way, mitlen, your Bob Prince avatar is wonderful, as is your quote -- I can still hear Bob saying: "We had 'em all the way!"