Nashville has a decent airport, but not spectacular. Good access to I-40 and also reasonable costs for parking compared to other airports. Also, the fact that Southwest is a major carrier in the Nashville market makes the flights competitive. Where the airport can improve is more on aesthetics. It really doesn't compare to the ambience and amenities of cities of similiar size -- Cincy, Orlando, etc...
Nashville is a toursim destination and should have a first-rate airport to reflect a first-rate city.
Pros: Interstate access, reasonable parking
Cons: long concourses, sterile appearance