I purchased a pre-owned Prius. It now has over 48,000 miles. My primary complaint is the exterior door material. If you barely hit the door, it leaves a mark or a ding (my car is white). Also, the interior is extremely difficult to keep clean. The armrests are very worn. The fabric seems cheap. Other than that, the car is great. I always average over 50 MPG. I routinely drive the car on the highway at speeds greater than 70 MPH and I still get great gas mileage. I traded in my Jeep (14 MPG) for the Prius and I'm so glad I did. The car is quiet, smooth and a joy to drive.
Other than the MPG, my favorite feature is the touch screen. I like the fact that it constantly reminds me of my MPG. It's like a game to me. My goal is to get a consistent MPG of 60. I'm almost there. Secondly, I like the smart key. No searching through my purse for the keys! It's great!
More durable interior fabric. Dent resistant doors like the Saturn vehicles. I believe they have the dent resistant materials for the door panels. Tint the rear windows as standard.