I've had three minor problems in the 10 months I've had the car, all cosmetic and all fixed under warranty, even though I might have contributed to two of them. First, see this PriusChat thread describing a problem with the instrument display:
http://priuschat.com/index.php?showtopic=19434&st=0
(The pictures I originally posted there are not available in my post, presumably because of a recent crash of that site.)
Second, the cowling below the driver's side windshield washer arm popped loose, causing the wiper arm to scrape on it.
Last, the plastic cover on the inside of the driver's-side "A" pillar popped loose. Frankly, I helped it along as I hurriedly got into the car (which I didn't mention to the dealer). I'm tall (6'4"), so my shoulder tends to run against the top edge of the door as I slide into the car. In this case, it grabbed the plastic cover too. The cover didn't come off completely; it was just slightly amiss.