I just traded in my '06 Aveo for my new Impala. I put 46,000 miles on it in the time that I owned it. I had only one issue with the car when I bought it, and it was minor - a defective rear window washer. After that warranty trip, the car was mechanically flawless. Unfortunately in my case, the car seemed to have a target on it, and I had it in repeatedly for minor body work. Once to repair scuff damage from a reckless driver passing me on the shoulder entering a construction zone, another to replace the front bumper skin, grille, and paint damage from a rock the size of a cantaloupe falling off of a rock truck, a third time to have dashboard scratches repaired from my neighbour's backpack, and a fourth time for paint work on the driver's rear corner when I ran over a nail that had something attached to it.
Keeping to a max speed of 55 mph, netted several 40 and higher mpg figures on solid highway only trips. My overall average was 35.3 mpg for the entire time I owned the car. Drive faster, and mileage will drop significantly.
Finally, the one notable issue that needs to be known about, is that the E-Tech engine in this car has weak timing belts. They had a history of premature failure when they were used in the Daewoo Lanos. I've heard of a few failures in the Aveo, but not as numerous as the earlier cars. The accepted workaround was to replace the belt at 50K miles instead of the scheduled 60k miles.