Well I didn't purchase it, but I was lucky enough to have parents that purchased my first car.
It was a 99, purchased in 01, that had been a rental. 22k or so miles. The guy we purchased it from had owned it for a year, meaning the rentals car company used it for a year, put 20k or so miles on it, then he bought it, got to putter around in a 1-year old car for a year and put low miles on it, then resell it at a decent amount, meaning he was constantly using a new car.
Worked great for me.
People do tend to ride rentals hard, but rental car companies want to keep providing customers with the newest cars, so you'll be picking up a car in pretty darn good shape.
I wouldn't hesitate to buy one again, if it was a good deal. (I just probably wouldn't, as an older one that has depreciated a bit more would serve me just as well.)