I watched a trailer. I am from Virginia, but not the Southwest part. Still, I felt the accents were over the top. Not so bad in the male leads, though. The worst one was Ashley Judd herself- a native of Kentucky.
Having grown up in that region, the actors' (especially Ashley Judd's) attempts at southwest Virginia accents just killed the authenticity for me. They sounded more like northerners making fun of southerns than actual southerners. I cringed every time they talked about getting "MURRied". One of the male actors (Anthony LaPaglia, I think) sounded legit, but he's the only main cast member who I think came close to getting it right. There was a part where one of the extras said two or three words in background at the pharmacy, and she nailed it. It wasn't just the accents, but also some of the dialect. For example, in over 20 years of living in that region, I don't think I ever heard an adult refer to their mother as "mama" or say that someone is "right pretty". It's "real pretty!"
I agree with your comments on not just the accents but the dialects as well. "MURRied" got to me too, big time! Odd that we should both think that LaPaglia got most of it right (although he did pronounce married as "MURRied" also) since he's not even from the U.S. More often than not movies of regional "flavor" come across as condescending due to the director's over-reliance on accent embellishment and their tendency to "over-quirk" their cast. On those two accounts, one such film that quickly comes to mind for me is "Steel Magnolias" (accent and quirk OVERLOAD!!). Another film, "Come Back to the 5 & Dime", contains two glaring dialect mishaps. 1) anyone born and raised in west Texas--especially then--would have said "fix" rather than "repair" and 2) would have said "baloney" and NEVER "balogna". I suppose we may be knit-picking though.