The points are OK but you also get points with Amex and if you sign up for the Amex rewards plus card, you get a 50% point bonus in the first year with average use that may equal the Diners bonus anyway.

Back to Diners I think the card appears to be more accepted in Europe. In Italy for example just about all gas stations and most tourist oriented vendors/sited do.
One other thing about car rentals, Amex and many other cards do not cover rental cars in Ireland, Italy and some other countries like Diners.
Get into an accident and the $80.00 will look like peanuts.
Mike