First, I'm glad I saw this post before doing my taxes this weekend (I want to get those refunds). I had no idea it wasn't deductible. Thanks for posting!
Second, I'm confused as to why the state made the change to TAVT. It used to be that you paid sales tax when you bought a car (4% to state, plus more to city and county--usually 7% or 8% total), and an annual tax based on the value of your vehicle (which I think went to the county). Now you don't pay a sales tax or an annual tax on the car, but you do pay this up front 6.75% value-based tax (TAVT) which I think goes to the state. If you bring in a car from another state you also have to pay the tax. If you lease you pay the tax, and then if you buy at the end of the lease you have to pay the tax again. And you can get a credit for the value of a car you trade-in, but only in the same transaction where you purchase a vehicle from a dealer. It just makes things confusing. Maybe it was a way to shift revenues from the counties to the state, since counties don't seem to get anything out of the vehicle taxes now. And to subsidize GA dealers (since buying out of state and bringing it into the state costs more, and the dealers can low-ball you even further on the trade-in because of the difference in taxes).