I've only heard great things about Nashville, so when I saw a cheap deal I knew I had to jump on it. And I'm glad I did! Nashville was kind of what I was expecting, kind of not. I will say that Nashville would be more fun as a trip with friends than a solo trip, but regardless I had a good time.
Surprisingly, I was able to do 90% of the things I wanted to do in 1 day by renting a car. There are some cool things to see, but where Nashville really shines is live music. I was impressed at how great the musicians were, and I'm not even a huge fan. Most of the shows are at night, but you may find something during the day!
In terms of getting around, it's easiest to stay in the downtown core or as close to it as you can. Public transportation wasn't too hard to use, but sometimes the buses were late. There is a bus that takes you straight from the Nashville Airport to downtown, but definitely look up the schedule beforehand if you're coming in super early or late. The frequency is only around ~45min - 1 hr per bus. The buses are fine around downtown but it's much easier to have a car. You can download the QuickTicket app to buy bus tickets and use them. Try to find a place to stay that lets you have free parking!
If I were to come again, I would make sure that I book my shows/viewings beforehand. There were a lot of places/people I wanted to see, but either 1) they were sold out or 2) the dates didn't line up with my schedule. But, I would definitely come again!
In terms of neighborhoods, I really liked the area around 12th South, The Gulch and Midtown! It's a super cute stretch that has a lot of cool murals. I would say that Music Row was alright, it was cool to drive past.
Other places I would recommend visiting (but didn't have the time) are the Country Music Hall of Fame & Museum, Ryman Auditorium & Grand Ole Opry.