The only Signature service I have used is "Visa Dining Privileges", which is just a free front end to Dinnerbroker: https://usa.visa.com/DinnerBroker/

I've used it before and it worked out well. Considering that DinnerBroker charges about $10 for most of those restaurants, it's nice to get it for free. You have to have either Visa Signature or Visa Infinite.

Perhaps you were thinking of Infinite - we have a definite issue of "card inflation", although I think that Visa has boxed themselves into a corner by calling the top one "infinite"!