As a southerner (Georgia, Florida's Redneck Riviera) who has lived 20+ years in Ohio, all I can say on the y'all front is that it is music to my ears, not heard enough in my daily life. My son, raised in Ohio, now in Texas, has almost become a southerner (he's trying hard) and has adopted y'all as a mainstay of his speech. He is doing reasonably well in applying it in sentences correctly. One of the cable channels (H2?) has a series on American slang and did an excellent show on Y'all as well as a good one on the contributions of the Scotts-Irish to the Americanized version of English.
In the northwestern part of Ohio (Celina) "you-uns" is frequently used. They also say "Please?" when they don't understand what you said. I had a heck of a time adopting to this idiom when first exposed to it, I was used to "Huh?", or "come again" And, around Deeeeeeetroit, if you are a southerner, you can expect the occasional "say something else, I want to hear you talk" comment, which does take some getting used to.