I shoot for 145 -- medium rare. Rare does not allow the connective tissues to dissolve and so is not as tender or flavorful.
Everyone around here likes well done. It's HARD cooking steaks well done without ruining them. I've had my best luck using rib eyes. Their high fat content keeps them juicy at higher temps.
My niece cooks all beef well done. Hard to chew and sort of sad. Great idea about the rib eyes. Never thought of that.