You got lucky on the ad velorum. You're supposed to pay that no matter what.
They were letting people choose which way they wanted to go at the tag office in the months prior to the cutover. You could stick with the old ad valorem system or the new title tax system depending on what worked out better for you. Now you can't choose. Ad valorem is gone but only the first owner of a new car really sees the benefit. If you buy used, it will take you roughly five years before you break even with what you would've paid in ad valorem- plus you pay it all at once now.