I only regret selling two vehicles. My 88 IROC, a cherry car but I didn't have any place to keep it in the apartment complex I lived in. And my 02 Trailblazer LTZ. The Trailblazer I had rebuilt the entire suspension on and it was a very clean, excellent running truck with only 90K miles on it, with a towing tune for the lower RPM torque. That I6, 4x4 with 3.73 gears got me 24.5 mpg average on a cross country trip.
The biggest disappointment was in the trade in price. If I had sold them privately I would have done better. If you trade in an 08, you're going to be very disappointed with what the dealer offers you if it's clean and in excellent mechanical condition.
I miss both of them though.