First, do not believe anyone who tells you Gallatin is a suburb. It isn't. I've lived in multiple suburbs of large cities and Gallatin is a small country city. Nothing north of Nashville is really nice but you could stretch and call Hendersonville a suburb. It ends there. Do not move to Gallatin expecting good restaurants or even good service or food at the chains. They can't even manage to execute fast food. The police force is focused on revenue while crime, especially property crime, is prevalent. They focus on patrolling the main highway through town along with some major streets. If you want your neighborhood patrolled, you have to pay them for driving through periodically. The amount of rudeness I've experienced here has largely come from this being a backwards, country area. Even Hendersonville is very different and it is only a few minutes away. Gallatin does have a few nice neighborhoods near Hendersonville. The school which is fed from these neighborhoods is probably okay. The Gallatin public schools though I couldn't imagine being good based on everything else we have experienced here. A lot of poverty and uneducated or undereducated are here. If you want country and are used to the small town that comes with it - the people, the lack of options, the police, property crime etc then Gallatin may be okay for you.
Gallatin also has a huge elderly population. If you over social security age, Gallatin may also be a place for you.
Do not move here from any city, suburb or nice small city or town. Just don't do it to yourself. Stop at Hendersonville if you have to live on the north side. I believe it would be worth the commute to find a Nashville neighborhood or one of the southern suburbs which are true suburbs.
Gallatin should never make a best places list. It is insane to even consider.