From a performance standpoint, the 540s are no longer anything special. I mean, Nissan Altimas, Mitsubishi Eclipses, etc all outperform the thing. So if thats the reason you want it - look elsewhere. (not saying that these other cars are better, I'm just showing you how a 'cheaper' vehicle outperforms the once pretty-awesome 540 because of dated technology.)
Breaking down when they get old? Isn't that what all machinery does? It really just depends on the owner's maintenance history. If they didnt take care of it - good luck. If they did... you'll have a wonderful car with many more miles to enjoy it through.