I was born and raised out of Nashville in Middle TN. I've now spent the last three years living in Knoxville. I'd recommend TN as a whole to you. Knoxville is a unique place as it blends the heritage of East TN / Appalachia with a university culture, a huge Department of Energy and Defense installation (Oak Ridge), and significant industry (Scripps Howard who runs HGTV is here along with TVA, medical companies, etc.). To top it off you have the Great Smokey National Park and the numerous lakes surrounding the area. While Knoxville isn't huge, the metro area is large enough to bring great performers and entertainment to the area -- James Taylor was here last week.
Allergies can be quite bad here as the city sits in a valley. This means all the allergens from the mountains hit the city. The good news is, folks can build up an immunity, eat local honey, or visit one of the world-class allergists in the city (we have a lot!). Most folks either build up a tolerance naturally over time, find some relief with OTC solutions like Flonase, etc. I actually found my allergies were worse when I lived in Atlanta than either in Middle or East TN. As long as you are OK being a little proactive in managing allergies, you'll be just fine. I know friends who swear natural honey (eating natural pollen) practically cured them. I've found my allergies are no more than seasonal and mild.
The area has a low COL, friendly neighbors, low crime, and strong faith communities. Quite a few people come here to retire or live 30-45 min away in one of the lakeside communities outside the city. The Knoxville airport has good connections to Delta, American, and United hubs. The prices are expensive, but they are working to become more competitive. Finally, healthcare here is excellent. The University of Tennessee medical school is in Memphis, but the teaching hospital is in Knoxville. On top of that, you have some top-notch private hospitals as well as some private practices leveraging connections to the Oak Ridge lab. For instance, the PET scan was developed by Oak Ridge folks. Now, the ProVision Proton therapy is a company that leverages some of those same connections.
If you have more specific questions, please feel free to let me know!