When I visited TN earlier this year for the first time, I really fell in love with Franklin, it has that small town appeal, friendly people, clean, low crime, etc. I went to some open houses, the realtor was a Californian who moved there 2 years earlier, and she says half of her buyers are from CA. Home prices are basically the same as in CA at this point, but i can definitely see the appeal of retiring there. I would say it's top 3 places I've visited so far that I would move after retirement, but I still have more places to reconnaissance.
I also visited Brentwood, and for the life of me I can't understand how homes there are so expensive. It's closer to Nashville than Franklin, but other than that it was very flat, no scenery, etc....and I saw a lot of homes for $6 million that I wouldn't even spend $2 million on given the location. I'm guessing maybe that's where the old money is.
I've also heard that East TN and West TN are like 2 different worlds, not sure how accurate that is, but I do plan on visiting East TN in the near future.