I just picked up a minivan today at Dollar (MCO). So far, so good. It does have 36,000 miles on it and a few dings but, otherwise, it is very clean, doesn't smell like smoke or anything and we've driven it around all day.
On another thread, I posted that I was told that most of the rental car companies have scaled back their fleet and are keeping cars in the fleet longer than they had been. I was also told by the agent that if you didn't have a reservation people weren't getting cars. When my mom was down in Orlando in June for a business trip, this was the case for many people. So, due to the economy, the rental cars have scaled back. You may find a similar situation with older cars at every place. Not sure.
Anyway, so far so good with my Dollar rental.