What is the perfect mileage for a used car?

It's tough to call... I'm looking into buying a used car, ditching my P.O.S. Mercury Sable. My price range is $8,000 - $10,000 but mileage is a concern. I have seen lower mileage vehicles (30,000) and higher mileage (90,000+). What range would be the best to go? Obviously if it's domestic or not can make a difference.. I only ask because with a lot of cars, you hit 60,000 and you have to start worrying about wheel bearings etc.. You get a car with higher mileage, chances are good that they've been replaced. Thanks for the insight!