Thanks for all the responses. I certainly agree with the point that some rigs go well beyond the "ten-year curse" if properly maintained. That's true of anything mechanical. The problem comes when you're buying something that (in this case) is 9 years old and you have no idea of the history of the unit. You have to assume the worst and be happy if you're wrong.
One of the best points I think I heard was...yeah, a $25K rig will have more problems than a new $250K rig will...but think how much repair/replace you can do for $225K! Great point Bill.