We purchased our Prius with 7,000 miles on it (original owner left country). It has performed exceptionally well except for the electronic issues that were repaired by removing and replacing the computer screen (Toyota covered it). Only other issue is Tires. The vehicle is heavier than most and you need to ensure that you purchase tires recommended by the owners guide to ensure that you do not risk the tire "rolling" onto the sidewall in a higher speed turn or situation where you must "dodge" an obstacle at higher speeds.
The ability to open and operate the car without "touching" a key device is a huge convenience factor along with the computer screen that relays fuel economy, etc. I love my indash map system (although it has a few quirks). We enjoy our Prius so much we now own a 2nd one (2005 model).
Leather seats would be a major improvement (much easier to clean). It would be nice to have the navigation system available for the passenger to operate while the car is in motion. You can't always pull off the road (traffic jams where you are crawling and need to find an alternate route).
† Edmunds.com received the highest numerical score in the proprietary J.D. Power 2014 Third-Party Automotive Website Evaluation Study℠. Results based on responses from 3,381 responses, measuring 14 companies and measures third-party automotive website usefulness among new and used vehicle shoppers. Proprietary study results are based on experiences and perceptions of owners surveyed from January 2014. Your experiences may vary. Visit jdpower.com.